Metal vanadium oxide particles

ABSTRACT

Laser pyrolysis can be used to produce directly metal vanadium oxide composite nanoparticles. To perform the pyrolysis a reactant stream is formed including a vanadium precursor and a second metal precursor. The pyrolysis is driven by energy absorbed from a light beam- Metal vanadium oxide nanoparticles can be incorporated into a cathode of a lithium based battery to obtain increased energy densities. Implantable defibrillators can be constructed with lithium based batteries having increased energy densities.

FIELD OF THE INVENTION

[0001] The invention relates to methods for producing particles of metalvanadium oxide powders through laser pyrolysis. In particular, theinvention relates to the use of laser pyrolysis for the production ofnanoscale metal vanadium oxide particles. The invention further relatesto batteries with improved performance that incorporate nanoscale metalvanadium oxides particles, such as silver vanadium oxide particles.

BACKGROUND OF THE INVENTION

[0002] Lithium based batteries have become commercially successful dueto their relatively high energy density. Suitable positive electrodematerials for lithium based batteries include materials that canintercalate lithium atoms into their lattice. The negative electrode canbe lithium metal lithium alloys or compounds that can reversiblyintercalate lithium atoms into their lattice. Batteries formed fromlithium metal or lithium alloy negative electrodes are referred to aslithium batteries while batteries formed with an anode (negativeelectrode) active material that can intercalate lithium ions arereferred to as lithium ion batteries.

[0003] In order to produce improved batteries, various materials havebeen examined for use as cathode (positive electrode) active materialsfor lithium based batteries. A variety of materials, generallychalcogenides, are useful in lithium based batteries. For example,vanadium oxides in certain oxidation states are effective materials forthe production of positive electrodes for lithium based batteries. Also,metal vanadium oxide compositions have been identified as having highenergy densities and high power densities, when used in positiveelectrodes for lithium based batteries. Silver vanadium oxide has aparticularly high energy density and high power densities, when used inlithium based batteries. Silver vanadium oxide batteries have foundparticular use in the production of implantable cardiac defibrillatorswhere the battery must be able to recharge a capacitor to deliver largepulses of energy in rapid succession, within ten seconds or less.

SUMMARY OF THE INVENTION

[0004] In a first aspect, the invention pertains to a method forproducing metal vanadium oxide particles comprising reacting a reactantstream comprising a vanadium precursor, and a second metal precursor ina reaction chamber. The reaction is driven by energy absorbed from anelectromagnetic field.

[0005] In another aspect, the invention pertains to a battery comprisinga cathode having active particles comprising silver vanadium oxide and abinder. The positive electrode exhibits an energy density of greaterthan about 340 milliampere hours per gram of active particles whendischarged to about 1.0 V.

[0006] In addition, the invention pertains to a battery comprising acathode having active particles comprising metal vanadium oxide and abinder, the positive electrode exhibiting an energy density of greaterthan about 400 milliampere hours per gram of active particles whendischarged to about 1.0V.

[0007] In a further aspect, the invention pertains to an implantabledefibrillator comprising a battery having a cathode comprising silvervanadium oxide with an energy density upon discharge to about 1.0V ofgreater than about 340 milliampere hours per gram of cathode activematerial.

[0008] Moreover, the invention pertains to a method of producing acomposite of elemental metal nanoparticles and vanadium oxidenanoparticles, the method comprising reacting a reactant streamcomprising a vanadium precursor, and a second metal precursor in areaction chamber, where the reaction is driven by energy absorbed froman electromagnetic field.

[0009] In another aspect, the invention pertains to a method forproducing metal vanadium oxide particles comprising reacting a reactantstream comprising a vanadium precursor, and a second metal precursor ina reaction chamber, where the reaction is driven by energy absorbed froma combustion flame.

[0010] In an additional aspect, the invention pertains to a collectionof particles comprising elemental metal selected from the groupconsisting of copper, silver, and gold, the particles, the collection ofparticles having an average particle size less than about 500 nm, andeffectively no particles have a diameter greater than about four timesthe average diameter.

[0011] In addition, the invention pertains to a method of producingparticles comprising a an elemental metal selected from the groupconsisting copper, silver and gold, the method comprising reacting amolecular stream in a reaction chamber, the molecular stream comprisinga metal precursor and a radiation absorber, where the reaction is drivenby electromagnetic radiation.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012]FIG. 1 is a schematic, sectional view of an embodiment of a laserpyrolysis apparatus, where the cross section is taken through the middleof the laser radiation path. The upper insert is a bottom-view of thecollection nozzle, and the lower insert is a top view of the deliverynozzle.

[0013]FIG. 2 is a schematic view of a reactant delivery apparatus forthe delivery of vapor reactants to the laser pyrolysis apparatus of FIG.1.

[0014]FIG. 3A is schematic, side view of a reactant delivery apparatusfor the delivery of an aerosol reactant to the laser pyrolysis apparatusof FIG. 1.

[0015]FIG. 3B is a schematic, side view of an alternative embodiment ofa reactant delivery apparatus for the delivery of an aerosol reactant tothe laser pyrolysis apparatus of FIG. 1.

[0016]FIG. 4 is a schematic, perspective view of an elongated reactionchamber for the performance of laser pyrolysis, where components of thereaction chamber are shown as transparent to reveal internal structure.

[0017]FIG. 5 is a sectional view of the reaction chamber of FIG. 4 takenalong line 5-5.

[0018]FIG. 6 is a schematic, sectional view of an apparatus for heattreating nanoparticles, in which the section is taken through the centerof the apparatus.

[0019]FIG. 7 is a schematic, sectional view of an oven for reactingnanoparticles under heat, in which the section is taken through themiddle of the oven.

[0020]FIG. 8 is a schematic, perspective view of an embodiment of abattery of the invention.

[0021]FIG. 9 is an x-ray diffractogram of crystalline VO₂ nanoparticles.

[0022]FIG. 10 is an x-ray diffractogram of crystalline V₂O₅nanoparticles produced by heat treating nanoparticles of crystallineVO₂.

[0023]FIG. 11 is a transmission electron microscope view of crystallineV₂O₅ nanoparticles.

[0024]FIG. 12 is a plot depicting the distribution of particle sizes forthe crystalline V₂O₅ nanoparticles depicted in FIG. 11.

[0025]FIG. 13 is a plot of four x-ray diffractograms of silver vanadiumoxide produced by heat treating nanocrystalline V₂O₅ with silver nitratein an oxygen atmosphere, where each diffractogram was produced withmaterials formed under different conditions.

[0026]FIG. 14 is a plot of four x-ray diffractograms of silver vanadiumoxide produced by heat treating nanocrystalline V₂O₅ with silver nitratein an argon atmosphere, where each diffractogram was produced withmaterials formed under different conditions.

[0027]FIG. 15 is a transmission electron microscope view of silvervanadium oxide nanoparticles.

[0028]FIG. 16 is a transmission electron microscope view of the V₂O₅nanoparticle samples used to produce the silver vanadium oxide particlesshown in FIG. 15.

[0029]FIG. 17 is an x-ray diffractogram of silver vanadium oxideproduced by heat treating a mixture of nanocrystalline VO₂ and silvernitrate powder in an oxygen atmosphere.

[0030]FIG. 18 is a plot of differential scanning calorimetrymeasurements obtained with samples with an x-ray diffractogram as shownin FIG. 17.

[0031]FIG. 19 is a plot of an x-ray diffractogram of mixed phasesilver—vanadium oxide materials produced directly by laser pyrolysissynthesis.

[0032]FIG. 20 is a transmission electron micrograph of silver—vanadiumoxide materials produced directly by laser pyrolysis synthesis, whichproduce an x-ray diffractogram as shown in FIG. 19.

[0033]FIG. 21 is an x-ray diffractogram of silver vanadium oxideparticles following a heat treatment in an oxygen atmosphere ofnanoscale silver—vanadium oxide materials as synthesized by laserpyrolysis.

[0034]FIG. 22 is a transmission electron micrograph of silver vanadiumoxide particles produced by heat treating nanoscale silver—vanadiumoxide materials.

[0035]FIG. 23 is a plot of two x-ray diffractograms of mixed phasematerials including silver vanadium oxide nanoparticles produceddirectly by laser pyrolysis, where each plot is produced with materialsproduced under slightly different conditions.

[0036]FIG. 24A is a transmission electron micrograph of the materialsfrom the sample corresponding to the upper diffractogram in FIG. 23.

[0037]FIG. 24B is a transmission electron micrograph of the materialsfrom the sample corresponding to the lower diffractogram in FIG. 23.

[0038]FIG. 25 is a plot of five x-ray diffractograms of mixed phasematerials including silver vanadium oxide nanoparticles produceddirectly by laser pyrolysis, where each plot is produced with materialsproduced with a different silver to vanadium ratio.

[0039]FIG. 26 is an x-ray diffractogram of elemental silvernanoparticles produced by laser pyrolysis under the conditions specifiedin the first column of Table 5.

[0040]FIG. 27 is an x-ray diffractogram of elemental silvernanoparticles produced by laser pyrolysis under the conditions specifiedin the second column of Table 5.

[0041]FIG. 28 is a transmission electron micrograph of the materialsfrom the sample corresponding to the diffractogram in FIG. 26.

[0042]FIG. 29 is a plot of voltage as a function of time for a lithiumbattery produced using silver vanadium oxide nanoparticles produced in aheat processing step described in Example 4.

[0043]FIG. 30 is a plot of voltage as a function of capacitycorresponding to the plot of voltage as a function of time shown in FIG.29.

[0044]FIG. 31 is a plot of voltage as a function of time for a lithiumbattery produced using mixed phase silver vanadium oxide nanoparticlesas produced directly by laser pyrolysis, as described in Example 5.

[0045]FIG. 32 is a plot of voltage as a function of capacitycorresponding to the plot of voltage as a function of time shown in FIG.31.

[0046]FIG. 33 is a plot of voltage as a function of time for a lithiumbattery produced using silver vanadium oxide nanoparticles followingheat treatment, as described in Example 6.

[0047]FIG. 34 is a plot of voltage as a function of capacitycorresponding to the plot of voltage as a function of time shown in FIG.33.

[0048]FIG. 35 is a plot of voltage as a function of time for a lithiumbattery produced using mixed phase silver vanadium oxide nanoparticles,as described in Example 7.

[0049]FIG. 36 is a plot of voltage as a function of capacitycorresponding to the plot of voltage as a function of time shown in FIG.35.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0050] Nanoscale metal vanadium oxide particles can be produced eitherdirectly through laser pyrolysis or by the application of laserpyrolysis to synthesize nanoscale vanadium oxide particles, which aresubjected subsequently to thermal/heat processing to form the metalvanadium oxide nanoparticles. Thus, metal vanadium oxides can beproduced directly by laser pyrolysis, where the laser pyrolysisreactants include precursors of vanadium as well as precursors of asecond metal. In addition, vanadium oxide nanoparticles can be used toform metal vanadium oxide nanoparticles, such as silver vanadium oxidenanoparticles, without losing the nanoscale size of the particles.Nanoscale metal vanadium oxide particles can be used to form batterieswith improved performance.

[0051] Vanadium oxide nanoparticles with various stoichiometries andcrystal structures can be produced by laser pyrolysis alone or withadditional processing. These various forms of vanadium oxidenanoparticles can be used as starting materials for the formation ofmetal vanadium oxide nanoparticles. The multiple metal nanoparticles areformed by mixing the vanadium oxide nanoparticles with a compound of themetal to be introduced into the vanadium oxide to form a material withboth metals in the lattice. By using appropriately selected processingconditions, the particles incorporating both metals can be formedwithout losing the nanoscale character of the initial vanadium oxidenanoparticles.

[0052] Preferred collections of metal vanadium oxide particles have anaverage diameter less than a micron and a very narrow distribution ofparticle diameters. In particular, the distribution of particlediameters preferably does not have a tail. In other words, there areeffectively no particles with a diameter an order of magnitude greaterthan the average diameter such that the particle size distributionrapidly drops to zero.

[0053] To generate vanadium oxide nanoparticle starting materials forfurther processing into metal vanadium oxides, laser pyrolysis is usedeither alone or in combination with additional processing. Specifically,laser pyrolysis has been found to be an excellent process forefficiently producing vanadium oxide nanoparticles with a narrowdistribution of average particle diameters. In addition, nanoscalevanadium oxide particles produced by laser pyrolysis can be subjected toheating under mild conditions in an oxygen environment or an inertenvironment to alter the crystal properties and/or the stoichiometry ofthe vanadium oxide particles without destroying the nanoparticle size.Thus, a variety of different types of vanadium oxide based nanoparticlescan be produced.

[0054] A basic feature of successful application of laser pyrolysis forthe production of vanadium oxide nanoparticles is production of areactant stream containing a vanadium precursor, a radiation absorberand an oxygen source. The reactant stream is pyrolyzed by an intenselight beam, such as a laser beam. The laser pyrolysis provides forformation of phases of materials that are difficult to form underthermodynamic equilibrium conditions. As the reactant stream leaves thelight beam, the vanadium oxide particles are rapidly quenched.

[0055] Starting with nanoscale vanadium oxide particles, metal vanadiumoxide particles can be formed by a thermal process. A second metalprecursor comprises a non-vanadium transition metal. Preferred secondmetal precursors include compositions with copper, silver or gold. Thesecond metal precursor compound is mixed with a collection of vanadiumoxide nanoparticles and heated to form the particles incorporating bothmetals. Under suitably mild conditions, the heat processing is effectiveto produce the particles while not destroying the nanoscale of theinitial vanadium oxide particles.

[0056] As noted above, a basic feature of the successful application oflaser pyrolysis for the direct production of metal vanadium oxidenanoparticles is the production of a reactant stream containing avanadium precursor, a precursor for a second metal, a radiation absorberand an oxygen source. The reactant stream is pyrolyzed by an intenselight beam, such as a laser beam or other intense light source. As thereactant stream leaves the light beam, the metal vanadium particles arerapidly quenched to yield metal vanadium oxide nanoparticles with ahighly uniform size distribution.

[0057] As noted above, lithium atoms and/or ions can intercalate intovarious forms of vanadium oxide and metal vanadium oxide particles. Toform a positive electrode, which acts as a cathode upon discharge of thecell, the metal vanadium oxide nanoparticles can be incorporated into aelectrode with a binder such as a polymer. The electrode preferablyincorporates additional electrically conductive particles held by abinder along with the metal vanadium oxide particles. The electrode canbe used as a positive electrode in a lithium battery or a lithium ionbattery. Lithium based batteries formed with cathodes includingnanoscale metal vanadium oxides have energy densities higher thantheoretical maximum values estimated for corresponding bulk metalvanadium oxides. In particular, metal vanadium oxides, specificallysilver vanadium oxides, have been produced with an energy densitygreater than about 340 milliampere hours per gram have been produced.Preferred metal vanadium oxide particles exhibit an energy densitygreater than about 350 milliampere hours per gram, and preferablygreater than about 360 milliampere hours per gram, and more preferablyfrom about 370 milliampere hours per gram to about 405 milliampere hoursper gram.

[0058] While the primary focus is on the use of laser pyrolysis for theproduction of metal vanadium oxide nanoparticles or precursors of metalvanadium oxide nanoparticles, the approaches described herein foraerosol precursor delivery can be adapted for other synthesisapproaches. In particular, the precursors can be used in a flamepyrolysis method. The precursor delivery approaches can be adapted for avariety of flame pyrolysis approaches. In one preferred approach, thereactant stream is directed into a hydrogen-oxygen flame. The flamesupplies the energy to drive the pyrolysis. Such a flame pyrolysisapproach should produce similar materials as the laser pyrolysistechniques herein, except that flame pyrolysis approaches generally donot produce a narrow particle size distribution.

[0059] While the focus herein is the production of ternary compoundsinvolving two metal constituents, approaches have also been discoveredto produce nanoparticles of group IB elemental metals with extremelyhigh uniformity. In particular, an example of the production ofelemental silver nanoparticles is provided below. Copper and gold, theother group IB elements, have similar chemistry, so that copper and goldnanoparticles can be produced by similar approaches.

[0060] A. Laser Pyrolysis For Nanoparticle Production

[0061] Laser pyrolysis has been discovered to be a valuable tool for theproduction of nanoscale vanadium oxide particles. In addition, theparticles produced by laser pyrolysis are a convenient material forfurther processing to expand the pathways for the production ofdesirable vanadium oxide particles. Thus, using laser pyrolysis alone orin combination with additional processes, a wide variety of vanadiumoxide particles can be produced. Furthermore, laser pyrolysis has beendiscovered to be a successful approach for the direct production ofmetal vanadium oxide particles.

[0062] The reaction conditions determine the qualities of the particlesproduced by laser pyrolysis. The reaction conditions for laser pyrolysiscan be controlled relatively precisely in order to produce particleswith desired properties. The appropriate reaction conditions to producea certain type of particles generally depend on the design of theparticular apparatus. Specific conditions used to produce vanadium oxideparticles in a particular apparatus are described below in the Examples.Additional information on the production of vanadium oxide nanoparticlesby laser pyrolysis is provided in copending and commonly assigned U.S.patent application Ser. No. 08/897,778 to Bi et al., entitled “VanadiumOxide Nanoparticles,” incorporated herein by reference. In addition,specific conditions for the direct production of silver vanadium oxideparticles by laser pyrolysis in a particular apparatus also aredescribed below in the Examples. Furthermore, some general observationson the relationship between reaction conditions and the resultingparticles can be made.

[0063] Increasing the laser power results in increased reactiontemperatures in the reaction region as well as a faster quenching rate.A rapid quenching rate tends to favor production of high energy phases,which may not be obtained with processes near thermal equilibrium.Similarly, increasing the chamber pressure also tends to favor theproduction of higher energy structures. Also, increasing theconcentration of the reactant serving as the oxygen source in thereactant stream favors the production of particles with increasedamounts of oxygen.

[0064] Reactant flow rate and velocity of the reactant gas stream areinversely related to particle size so that increasing the reactant gasflow rate or velocity tends to result in smaller particle size. Also,the growth dynamics of the particles have a significant influence on thesize of the resulting particles. In other words, different forms of aproduct compound have a tendency to form different size particles fromother phases under relatively similar conditions. Laser power alsoinfluences particle size with increased laser power favoring largerparticle formation for lower melting materials and smaller particleformation for higher melting materials.

[0065] Laser pyrolysis has been performed generally with gas phasereactants. The use of exclusively gas phase reactants is somewhatlimiting with respect to the types of precursor compounds that can beused. Thus, techniques have been developed to introduce aerosolscontaining reactant precursors into laser pyrolysis chambers. Theaerosol atomizers can be broadly classified as ultrasonic atomizers,which use an ultrasonic transducer to form the aerosol, or as mechanicalatomizers, which use energy from one or more flowing fluids (liquids,gases, or supercritical fluids) themselves to form the aerosol. Improvedaerosol delivery apparatuses for reactant systems, including laserpyrolysis apparatuses, are described further in copending and commonlyassigned U.S. patent application Ser. No. 09/188,670 to Gardner et al.,entitled “Reactant Delivery Apparatuses,” incorporated herein byreference.

[0066] Using aerosol delivery apparatuses, solid precursor compounds canbe delivered by dissolving the compounds in a solvent. Alternatively,powdered precursor compounds can be dispersed in a liquid\solvent foraerosol delivery. Liquid precursor compounds can be delivered as anaerosol from a neat liquid, a liquid/gas mixture, liquid mixtures or aliquid solution, if desired. Aerosol reactants can be used to obtainsignificant reactant throughput. The solvent, if any, can be selected toachieve desired properties of the solution Suitable solvents includewater, methanol, ethanol and other organic solvents The solvent shouldhave a desired level of purity such that the resulting particles have adesired purity level.

[0067] If the aerosol precursors are formed with a solvent present, thesolvent is rapidly evaporated by the laser beam in the reaction chambersuch that a gas phase reaction can take place. Thus, the fundamentalfeatures of the laser pyrolysis reaction are unchanged. However, thereaction conditions are affected by the presence of the aerosol.Suitable conditions for the formation of manganese oxide nanoparticlesby laser pyrolysis with aerosol precursors are described in copendingand commonly assigned U.S. patent application Ser. No. 09/188,770, filedon Nov. 9, 1998, entitled “Metal Oxide Particles,” incorporated hereinby reference. Suitable conditions for the production of silver vanadiumoxide particles by laser pyrolysis with aerosol precursors are describedin the Examples below.

[0068] Suitable vanadium precursors for aerosol production include, forexample, vanadium trichloride (VCl₃), vanadyl trichloride (VOCl₃),vanadyl sulfate hydrate (VOSO₄.H₂O), ammonium vanadate (NH₄VO₃),vanadium oxide compounds (e.g., V₂O₅ and V₂O₃, which are soluble inaqueous nitric acid), and vanadyl dichloride (VOCl₂), which is solublein absolute alcohol. Suitable silver precursors include, for example,silver sulfate (Ag₂SO₄), silver carbonate (Ag₂CO₃), silver nitrate(AgNO₃), silver chlorate (AgClO₃) and silver perchlorate (AgClO₄).Suitable copper precursors include, for example, cupric nitrate(Cu(NO₃)₂), cupric chloride (CuCl₂), cuprous chloride (CuCl) and cupricsulfate (CuSO₄) . Suitable gold precursors include, for example, goldtrichloride (AuCl₃) and gold powder.

[0069] The compounds are dissolved in a solution preferably with aconcentration greater than about 0.1 molar. Generally, the greater theconcentration of precursor in the solution the greater the throughput ofreactant through the reaction chamber. As the concentration increases,however, the solution can become more viscous such that the aerosol hasdroplets with larger sizes than desired. Thus, selection of solutionconcentration can involve a balance of factors in the selection of apreferred solution concentration.

[0070] Appropriate vanadium precursor compounds for vapor deliverygenerally include vanadium compounds with reasonable vapor pressures,i.e., vapor pressures sufficient to get desired amounts of precursorvapor in the reactant stream. The vessel holding a solid or liquidvanadium precursor compound can be heated to increase the vapor pressureof the vanadium precursor, if desired. Suitable vanadium precursorsinclude, for example, VCl₄, VOCl₂, V(CO)₆ and VOCl₃. The chlorine inthese representative precursor compounds can be replaced with otherhalogens, e.g., Br, I and F.

[0071] For the production of metal vanadium oxide particles, suitablemetal precursors have sufficient vapor pressure to obtain desiredamounts of metal precursor vapor in the reactant stream. Suitable copperprecursors for vapor delivery include, for example, cupric chloride(CuCl₂) . Suitable silver precursors for vapor delivery include, forexample, silver chloride (AgCl). Alternatively, one of the vanadiumprecursor and metal precursor can be delivered as an aerosol while theother is delivered as a vapor. In particular, the metal precursor, suchas a silver precursor, can be delivered as an aerosol while the vanadiumprecursor is delivered as a vapor.

[0072] For the production of mixed metal oxides with two or more metals,the relative amounts of the metals in the reactant stream can be alteredto vary the relative amounts of metal in the resulting compositions. Thephase diagram for mixed metal oxides is necessarily more complex thancorresponding phase diagrams for metal oxides. Thus, the addition of arelatively larger amount of one metal relative to the other can resultin production of phases with increased amounts of that metal, either asa major phase or as a larger relative quantity in a mixed phase product.

[0073] Therefore, the stoichiometry of the product particles can bealtered by varying the relative amounts of metals within the solution ordispersion for aerosol delivery. Similar results can be obtained bydelivering the metal precursors as two or more separate aerosols, wherethe relative amounts of metal precursors can be varied by changing theconcentrations of the metals in the liquid and/or by the relativeamounts of aerosol. Furthermore, one or more of the metal precursors canbe delivered in a vapor state, and the relative amounts of metal can beappropriately adjusted to obtain a desired product.

[0074] Preferred reactants serving as oxygen source include, forexample, O₂, CO, CO₂, O₃ and mixtures thereof. The reactant compoundserving as the oxygen source should not react significantly with thevanadium precursor or other metal precursor prior to entering thereaction zone since this generally would result in the formation oflarge particles.

[0075] Laser pyrolysis can be performed with a variety of optical lightfrequencies. Preferred light sources include lasers, especially lasersthat operate in the infrared portion of the electromagnetic spectrum.CO₂ lasers are particularly preferred sources of light. Infraredabsorbers for inclusion in the molecular stream include, for example,C₂H₄, isopropyl alcohol (CH₃CHOHCH₃), NH₃, SF₆, SiH₄ and O₃. O₃ can actas both an infrared absorber and as an oxygen source. Alternatively, asolvent, such as isopropyl alcohol, in a liquid delivered by aerosol canabsorb light from the light beam. The radiation absorber, such as theinfrared absorber, absorbs energy from the radiation beam anddistributes the energy to the other reactants to drive the pyrolysis.

[0076] Preferably, the energy absorbed from the radiation beam increasesthe temperature at a tremendous rate, many times the rate that energygenerally would be produced even by strongly exothermic reactions undercontrolled condition. While the process generally involvesnonequilibrium conditions, the temperature can be describedapproximately based on the heat in the absorbing region. The laserpyrolysis process is qualitatively different from the process in acombustion reactor where an energy source initiates a reaction, but thereaction is driven by energy given off by an exothermic reaction.

[0077] An inert shielding gas can be used to reduce the amount ofreactant and product molecules contacting the reactant chambercomponents. Appropriate shielding gases include, for example, Ar, He andN₂. Inert gas can also be mixed with the reactant stream to moderate thereaction.

[0078] An appropriate laser pyrolysis apparatus generally includes areaction chamber isolated from the ambient environment. A reactant inletconnected to a reactant supply system produces a reactant stream throughthe reaction chamber. A light beam path intersects the reactant streamat a reaction zone. The is reactant/product stream continues after thereaction zone to an outlet, where the reactant/product stream exits thereaction chamber and passes into a collection system. Generally, thelight source is located external to the reaction chamber, and the lightbeam enters the reaction chamber through an appropriate window.

[0079] Referring to FIG. 1, a particular embodiment 100 of a laserpyrolysis apparatus involves a reactant supply system 102, reactionchamber 104, collection system 106, light source 108 and shieldinggas-delivery system 110. Two alternative reaction supply systems can beused with the apparatus of FIG. 1. The first reaction supply system isused to deliver exclusively gaseous reactants. The second reactantsupply system is used to deliver one or more reactants as an aerosol.Variations on these reaction supply systems can also be used.

[0080] Referring to FIG. 2, a first embodiment 112 of reactant supplysystem 102 includes a source 120 of vanadium precursor compound. Forliquid or solid vanadium precursors, a carrier gas from carrier gassource 122 can be introduced into precursor source 120 to facilitatedelivery of the vanadium precursor as a vapor. The carrier gas fromsource 122 preferably is either an infrared absorber or an inert gas andis preferably bubbled through a liquid precursor compound or deliveredinto a solid precursor delivery system. Inert gas used as a carrier gascan moderate the reaction conditions. The quantity of precursor vapor inthe reaction zone is roughly proportional to the flow rate of thecarrier gas.

[0081] Alternatively, carrier gas can be supplied directly from infraredabsorber source 124 or inert gas source 126, as appropriate Anadditional reactant, such as an oxygen source, is supplied from reactantsource 128, which can be a gas cylinder or other suitable container. Thegases from the precursor source 120 are mixed with gases from reactantsource 128, infrared absorber source 124 and inert gas source 126 bycombining the gases in a single portion of tubing 130. The gases arecombined a sufficient distance from reaction chamber 104 such that thegases become well mixed prior to their entrance into reaction chamber104.

[0082] The combined gas in tube 130 passes through a duct 132 intorectangular channel 134, which forms part of an injection nozzle fordirecting reactants into the reaction chamber. Portions of reactantsupply system 112 can be heated to inhibit the deposition of precursorcompound on the walls of the delivery system.

[0083] A metal precursor can be supplied from metal precursor source138, which can be a liquid reactant delivery apparatus, a solid reactantdelivery apparatus, a gas cylinder or other suitable container orcontainers. If metal precursor source 138 delivers a liquid or solidreactant, carrier gas from carrier gas source 122 or an alternativecarrier gas source can be used to facilitate delivery of the reactant.As shown in FIG. 2, metal precursor source 138 delivers a metalprecursor to duct 132 by way of tubing 130.

[0084] Flow from sources 122, 124, 126 and 128 are preferablyindependently controlled by mass flow controllers 136. Mass flowcontrollers 136 preferably provide a controlled flow rate from eachrespective source. Suitable mass flow controllers include, for example,Edwards Mass Flow Controller, Model 825 series, from Edwards High VacuumInternational, Wilmington, Mass.

[0085] Referring to FIG. 3A, an alternative embodiment 150 of thereactant supply system 102 is used to supply an aerosol to channel 134.As described above, channel 134 forms part of an injection nozzle fordirecting reactants into the reaction chamber through the reactantinlet. Reactant supply system 150 includes an aerosol generator 152,carrier gas/vapor supply tube 154 and junction 156. Channel 134, aerosolgenerator 152 and supply tube 154 meet within interior volume 158 ofjunction 156. Supply tube 154 is oriented to direct carrier gas alongchannel 134. Aerosol generator 152 is mounted such that an aerosol 160is generated in the volume of chamber 158 between the opening intochannel 134 and the outlet from supply tube 154.

[0086] Aerosol generator 152 can operate based on a variety ofprinciples. For example, the aerosol can be produced with an ultrasonicnozzle, with an electrostatic spray system, with a pressure-flow orsimplex atomizer, with an effervescent atomizer or with a gas atomizerwhere liquid is forced under significant pressure through a smallorifice and sheared into droplets by a colliding gas stream. Suitableultrasonic nozzles can include piezoelectric transducers. Ultrasonicnozzles with piezoelectric transducers and suitable broadband ultrasonicgenerators are available from Sono-Tek Corporation, Milton, N.Y., suchas model 8700-120. Suitable aerosol generators are described further incopending and commonly assigned, U.S. patent application Ser. No.09/188,670 to Gardner et al., entitled “REACTANT DELIVERY APPARATUSES,”incorporated herein by reference. Additional aerosol generators can beattached to junction 156 through other ports 162 such that additionalaerosols can be generated in interior 158 for delivery into the reactionchamber.

[0087] Junction 156 includes ports 162 to provide access from outsidejunction 156 to interior 158. Thus, channel 134, aerosol generator 152and supply Tube 154 can be mounted appropriately. In one embodiment,junction 156 is cubic with six cylindrical ports 162, with one port 162extending from each face of junction 156. Junction 156 can be made fromstainless steel or other durable, noncorrosive material. A window 161preferably is sealed at one port 162 to provide for visual observationinto interior 158. The port 162 extending from the bottom of junction156 preferably includes a drain 163, such that condensed aerosol that isnot delivered through channel 134 can be removed from junction 156.

[0088] Carrier gas/vapor supply tube 154 is connected to gas source 164.Gas source 164 can include a plurality of gas containers, liquidreactant delivery apparatuses, and/or a solid reactant deliveryapparatuses, which are connected to deliver a selected gas or gasmixture to supply tube 154. Thus, carrier gas/vapor supply tube 154 canbe used to deliver a variety of desired gases and/or vapors within thereactant stream including, for example, laser absorbing gases,reactants, and/or inert gases. The flow of gas from gas source 164 tosupply tube 154 preferably is controlled by one or more mass flowcontrollers 166. Liquid supply tube 168 is connected to aerosolgenerator 152. Liquid supply tube 168 is connected to liquid supply 170.

[0089] For the production of vanadium oxide particles, liquid supply 170can hold a liquid comprising a vanadium precursor. For the production ofmetal vanadium oxide particles, liquid supply 170 preferably holds aliquid comprising both a vanadium precursor and a metal precursor.Alternatively, for the production of metal vanadium oxide particles,liquid supply 170 can hold a liquid comprising metal precursor whilevanadium precursor is delivered by way of vapor supply tube 154 and gassource(s) 164. Similarly, if desired, liquid supply 170 can hold aliquid comprising vanadium precursor, while metal precursor is deliveredby way of vapor supply tube 154 and gas source(s) 164. Also, twoseparate aerosol generators 152 can be used to generate aerosol withinjunction 156, with one producing an aerosol with vanadium precursor andthe second producing aerosol with the metal precursor.

[0090] In the embodiment shown in FIG. 3, aerosol generator 152generates an aerosol with momentum roughly orthogonal to the carrier gasflow from tube 154 to channel 134. Thus, carrier gas/vapor from supplytube 154 directs aerosol precursor generated by aerosol generator 152into channel 134. In operation, carrier gas flow directs the aerosoldelivered within chamber 158 into channel 134. In this way, the deliveryvelocity of the aerosol is determined effectively by the flow rate ofthe carrier gas.

[0091] In alternative preferred embodiments, the aerosol generator isplaced at an upward angle relative to the horizontal, such that acomponent of the forward momentum of the aerosol is directed alongchannel 134. In a preferred embodiment, the output directed from theaerosol generator is placed at about a 45° angle relative to the normaldirection defined by the opening into channel 134, i.e. the direction ofthe flow into channel 134 from supply tube 154.

[0092] Referring to FIG. 3B, another embodiment 172 of the reactantsupply system 102 can be used to supply an aerosol to channel 134.Reactant supply system 172 includes an outer nozzle 174 and an innernozzle 176. Outer nozzle 174 has an upper channel 178 that leads to a ⅝in. by ¼ in. rectangular outlet 180 at the top of outer nozzle 174, asshown in the insert in FIG. 3B. Outer nozzle 174 includes a drain tube183 in base plate 184. Drain tube 183 is used to remove condensedaerosol from outer nozzle 174. Inner nozzle 176 is secured to outernozzle 174 at fitting 185.

[0093] Inner nozzle 176 is a gas atomizer from Spraying Systems(Wheaton, Ill.). The inner nozzle has about a 0.5 inch diameter and a12.0 inch length. The top of the nozzle is a twin orifice internal mixatomizer 186 (0.055 in. gas oriface and 0.005 in. liquid oriface).Liquid is fed to the atomizer through tube 187, and gases forintroduction into the reaction chamber are fed to the atomizer throughtube 188. Interaction of the gas with the liquid assists with dropletformation.

[0094] Outer nozzle 174 and inner nozzle 176 are assembledconcentrically. Outer nozzle 174 shapes the aerosol generated by innernozzle 176 such that it has a flat rectangular cross section. Inaddition, outer nozzle 174 helps to achieve a uniform aerosol velocityand a uniform aerosol distribution along the cross section. Outer nozzle174 can be reconfigured for different reaction chambers.

[0095] Referring to FIG. 1, shielding gas delivery system 110 includesinert gas source 190 connected to an inert gas duct 192. Inert gas duct192 flows into annular channel 194. A mass flow controller 196 regulatesthe flow of inert gas into inert gas duct 192. If reactant deliverysystem 112 is used, inert gas source 126 can also function as the inertgas source for duct 192, if desired.

[0096] The reaction chamber 104 includes a main chamber 200. Reactantsupply system 102 connects to the main chamber 200 at injection nozzle202. Reaction chamber 104 can be heated to keep the precursor compoundin the vapor state. Similarly, the argon shielding gas preferably can beheated. The chamber can be examined for condensation to ensure thatprecursor is not deposited in the chamber.

[0097] The end of injection nozzle 202 has an annular opening 204 forthe passage of inert shielding gas, and a reactant inlet 206 for thepassage of reactants to form a reactant stream in the reaction chamber.Reactant inlet 206 preferably is a slit, as shown in FIG. 1. Annularopening 204 has, for example, a diameter of about 1.5 inches and a widthalong the radial direction from about ⅛ in to about {fraction (1/16)}in. The flow of shielding gas through annular opening 204 helps toprevent the spread of the reactant gases and product particlesthroughout reaction chamber 104.

[0098] Tubular sections 208, 210 are located on either side of injectionnozzle 202. Tubular sections 208, 210 include ZnSe windows 212, 214,respectively. Windows 212, 214 are about 1 inch in diameter. Windows212, 214 are preferably cylindrical lenses with a focal length equal tothe distance between the center of the chamber to the surface of thelens to focus the beam to a point just below the center of the nozzleopening. Windows 212, 214 preferably have an antireflective coating.Appropriate ZnSe lenses are available from Janos Technology, Townshend,Vt. Tubular sections 208, 210 provide for the displacement of windows212, 214 away from main chamber 200 such that windows 212, 214 are lesslikely to be contaminated by reactants and/or products. Window 212, 214are displaced, for example, about 3 cm from the edge of the main chamber200.

[0099] Windows 212, 214 are sealed with a rubber o-ring to tubularsections 208, 210 to prevent the flow of ambient air into reactionchamber 104. Tubular inlets 216, 218 provide for the flow of shieldinggas into tubular sections 208, 210 to reduce the contamination ofwindows 212, 214. Tubular inlets 216, 218 are connected to inert gassource 138 or to a separate inert gas source. In either case, flow toinlets 216, 218 preferably is controlled by a mass flow controller 220.

[0100] Light source 108 is aligned to generate a light beam 222 thatenters window 212 and exits window 214. Windows 212, 214 define a lightpath through main chamber 200 intersecting the flow of reactants atreaction zone 224. After exiting window 214, light beam 222 strikespower meter 226, which also acts as a beam dump. An appropriate powermeter is available from Coherent Inc., Santa Clara, Calif. Light source108 preferably is a laser, although it can be an intense conventionallight source such as an arc lamp. Preferably, light source 108 is aninfrared laser, especially a CW CO₂ laser such as an 1800 watt maximumpower output laser available from PRC Corp., Landing, N.J. Inalternative embodiments, light source 108 is replaced by another type ofelectromagnetic energy source such as a microwave generator. In thisembodiment, the reactant stream includes a radiation absorbing compound,such as a microwave absorber.

[0101] Reactants passing through reactant inlet 206 in injection nozzle202 initiate a reactant stream. The reactant stream passes throughreaction zone 224, where reaction involving the precursor and additionalreactant compound(s) takes place. Heating of the gases in reaction zone224 generally is extremely rapid, roughly on the order of 10⁵ degreeC/sec depending on the specific conditions. The reaction is rapidlyquenched upon leaving reaction zone 224, and particles 228 are formed inthe reactant stream. The nonequilibrium nature of the process allows forthe production of nanoparticles with a highly uniform size distributionand structural homogeneity.

[0102] The path of the reactant/product stream continues to collectionnozzle 230. Collection nozzle 230 is spaced about 2 cm from injectionnozzle 202. The small spacing between injection nozzle 202 andcollection nozzle 230 helps reduce the contamination of reaction chamber104 with reactants and products. Collection nozzle 230 has a circularopening 232. Circular opening 232 feeds into collection system 106.

[0103] The chamber pressure is monitored with a pressure gauge attachedto the main chamber. The preferred chamber pressure for the productionof the desired oxides generally ranges from about 80 Torr to about 500Torr.

[0104] Reaction chamber 104 has two additional tubular sections notshown. One of the additional tubular sections projects into the plane ofthe sectional view in FIG. 1, and the second additional tubular sectionprojects out of the plane of the sectional view in FIG. 1. When viewedfrom above, the four tubular sections are distributed roughly,symmetrically around the center of the chamber. These additional tubularsections have windows for observing the inside of the chamber. In thisconfiguration of the apparatus, the two additional tubular sections arenot used to facilitate production of particles.

[0105] Collection system 106 preferably includes a curved channel 270leading from collection nozzle 230. Because of the small size of theparticles, the product particles follow the flow of the gas aroundcurves. Collection system 106 includes a filter 272 within the gas flowto collect the product particles. Due to curved section 270, the filteris not supported directly above the chamber. A variety of materials suchas Teflon, glass fibers and the like can be used for the filter as longas the material is inert and has a fine enough mesh to trap theparticles. Preferred materials for the filter include, for example, aglass fiber filter from ACE Glass Inc., Vineland, N.J. and cylindricalNomex® fiber filters from AF Equipment Co., Sunnyvale, Calif.

[0106] Pump 274 is used to maintain collection system 106 at a selectedpressure. A variety of different pumps can be used. Appropriate pumpsfor use as pump 274 include, for example, Busch Model B0024 pump fromBusch, Inc., Virginia Beach, Va. with a pumping capacity of about 25cubic feet per minute (cfm) and Leybold Model SV300 pump from LeyboldVacuum Products, Export, Pa. with a pumping capacity of about 195 cfm.It may be desirable to flow the exhaust of the pump through a scrubber276 to remove any remaining reactive chemicals before venting into theatmosphere. The entire apparatus 100 can be placed in a fume hood forventilation purposes and for safety considerations. Generally, the laserremains outside of the fume hood because of its large size.

[0107] The apparatus is controlled by a computer. Generally, thecomputer controls the laser and monitors the pressure in the reactionchamber. The computer can be used to control the flow of reactantsand/or the shielding gas. The pumping rate is controlled by either amanual needle valve or an automatic throttle valve inserted between pump274 and filter 272. As the chamber pressure increases due to theaccumulation of particles on filter 272, the manual valve or thethrottle valve can be adjusted to maintain the pumping rate and thecorresponding chamber pressure.

[0108] The reaction can be continued until sufficient particles arecollected on filter 272 such that the pump can no longer maintain thedesired pressure in the reaction chamber 104 against the resistancethrough filter 272. When the pressure in reaction chamber 104 can nolonger be maintained at the desired value, the reaction is stopped, andfilter 272 is removed. With this embodiment, about 1-300 grams ofparticles can be collected in a single run before the chamber pressurecan no longer be maintained. A single run generally can last up to about10 hours depending on the reactant delivery system, the type of particlebeing produced and the type of filter being used.

[0109] The reaction conditions can be controlled relatively precisely.In particular, the mass flow controllers are quite accurate. The lasergenerally has about 0.5 percent power stability. With either a manualcontrol or a throttle valve, the chamber pressure can be controlled towithin about 1 percent.

[0110] The configuration of the reactant supply system 102 and thecollection system 106 can be reversed. In this alternativeconfiguration, the reactants are supplied from the top of the reactionchamber, and the product particles are collected from the bottom of thechamber. In this configuration, the collection system may not include acurved section so that the collection filter is mounted directly belowthe reaction chamber.

[0111] An alternative design of a laser pyrolysis apparatus has beendescribed in copending and commonly assigned U.S. patent applicationSer. No. 08/808,850, entitled “Efficient Production of Particles byChemical Reaction,” incorporated herein by reference. This alternativedesign is intended to facilitate production of commercial quantities ofparticles by laser pyrolysis. The reaction chamber is elongated alongthe laser beam in a dimension perpendicular to the reactant stream toprovide for an increase in the throughput of reactants and products. Theoriginal design of the apparatus was based on the introduction of purelygaseous reactants. Alternative embodiments for the introduction of anaerosol into an elongated reaction chamber is described in copending andcommonly assigned U.S. patent application Ser. No. 09/188,670 to Gardneret al., filed on Nov. 9, 1998, entitled “Reactant Delivery Apparatuses,”incorporated herein by reference.

[0112] In general, the alternative pyrolysis apparatus includes areaction chamber designed to reduce contamination of the chamber walls,to increase the production capacity and to make efficient use ofresources. To accomplish these objectives, an elongated reaction chamberis used that provides for an increased throughput of reactants andproducts without a corresponding increase in the dead volume of thechamber. The dead volume of the chamber can become contaminated withunreacted compounds and/or reaction products.

[0113] The design of the improved reaction chamber 300 is shownschematically in FIGS. 4 and 5. A reactant inlet 302 enters the mainchamber 304. Reactant inlet 302 provides for the introduction of gaseousand/or aerosol reactants into main chamber 304. Reactant inlet 302conforms generally to the shape of main chamber 304. The introduction ofreactants through reactant inlet 302 for the production of vanadiumoxide particles or metal vanadium oxide particles can be performed byfollowing the discussion above regarding the introduction of aerosoland/or vapor precursors with the laser pyrolysis apparatus of FIG. 1,appropriately adapted for the alternative structure of the reactantinlet.

[0114] Main chamber 304 includes an outlet 306 along thereactant/product stream for removal of particulate products, anyunreacted gases and inert gases. Shielding gas inlets 310 are located onboth sides of reactant inlet 302. Shielding gas inlets are used to forma blanket of inert gases on the sides of the reactant stream to inhibitcontact between the chamber walls and the reactants and products.

[0115] Tubular sections 320, 322 extend from the main chamber 304.Tubular sections 320, 322 hold windows 324, 326 to define a laser beampath 328 through the reaction chamber 300. Tubular sections 320, 322 caninclude inert gas inlets 330, 332 for the introduction of inert gas intotubular sections 320, 322.

[0116] The dimensions of elongated reactant inlet 316 preferably aredesigned for high efficiency particle production. Reasonable dimensionsfor the reactant inlet for the production of vanadium oxidenanoparticles and metal vanadium oxide nanoparticles, when used with a1800 watt CO₂ laser, are from about 5 mm to about 1 meter.

[0117] The improved apparatus includes a collection system to remove thenanoparticles from the molecular stream. The collection system can bedesigned to collect a large quantity of particles without terminatingproduction or, preferably, to run in continuous production by switchingbetween different particle collectors within the collection system. Thecollection system can include curved components within the flow pathsimilar to curved portion of the collection system shown in FIG. 1.

[0118] A preferred embodiment of a collection system for particleproduction systems operating in a continuous collection mode isdescribed in copending and commonly assigned U.S. patent applicationSer. No. 09/107,729 to Gardner et al., entitled “Particle CollectionApparatus And Associated Methods,” incorporated herein by reference. Abatch collection system for use with the improved reaction system isdescribed in copending and commonly assigned U.S. patent applicationSer. No. 09/188,770, filed on Nov. 9, 1998, entitled “Metal OxideParticles,” incorporated herein by reference. The configuration of thereactant injection components and the collection system can be reversedsuch that the particles are collected at the top of the apparatus.

[0119] As noted above, properties of the vanadium oxide particles andmetal vanadium oxide particles can be modified by further processing.Suitable starting material for the heat treatment include vanadium oxideparticles and metal vanadium oxide particles produced by laserpyrolysis. Suitable vanadium oxide materials include, for example, VO,VO_(1.27), VO₂, V₂O₃, V₃O₅, V₄O₉, V₆O₁₃, and amorphous V₂O₅. Similarly,the starting materials can be metal vanadium oxide particles, such assilver vanadium oxide particles and/or copper vanadium oxide particlesproduced by laser pyrolysis. Suitable metal vanadium oxide materialsinclude Ag₂V₄O₁₁ and a new crystalline form of silver vanadium oxidedescribed in the Examples below. In addition, particles used as startingmaterial can have been subjected to one or more prior heating stepsunder different conditions.

[0120] The starting materials generally can be particles of any size andshape, although nanoscale particles are preferred starting materials.The nanoscale particles have an average diameter of less than about 1000nm and preferably from about 5 nm to about 500 nm, and more preferablyfrom about 5 nm to about 150 nm. Suitable nanoscale starting materialshave been produced by laser pyrolysis.

[0121] The vanadium oxide particles or metal vanadium oxide particlesare preferably heated in an oven or the like to provide generallyuniform heating. The processing conditions generally are mild, such thatsignificant amounts of particle sintering does not occur. Thetemperature of heating preferably is low relative to the melting pointof both the starting material and the product material.

[0122] For certain target product particles, additional heating does notlead to further variation in the particle composition once equilibriumhas been reached. The atmosphere for the heating process can be anoxidizing atmosphere or an inert atmosphere. In particular, forconversion of amorphous particles to crystalline particles or from onecrystalline structure to a different crystalline structure ofessentially the same stoichiometry, the atmosphere generally can beinert. The atmosphere over the particles can be static, or gases can beflowed through the system.

[0123] Appropriate oxidizing gases include, for example, O₂, O₃, CO,CO₂, and combinations thereof. The O₂ can be supplied as air. Oxidizinggases optionally can be mixed with inert gases such as Ar, He and N₂.When inert gas is mixed with the oxidizing gas, the gas mixture caninclude from about 1 percent oxidizing gas to about 99 percent oxidizinggas, and more preferably from about 5 percent oxidizing gas to about 99percent oxidizing gas. Alternatively, either essentially pure oxidizinggas or pure inert gas can be used, as desired.

[0124] The precise conditions can be altered to vary the type ofvanadium oxide product or metal vanadium oxide produce that is produced.For example, the temperature, time of heating, heating and coolingrates, the gases and the exposure conditions with respect to the gasescan all be changed, as desired. Generally, while heating under anoxidizing atmosphere, the longer the heating period the more oxygen thatis incorporated into the material, prior to reaching equilibrium. Onceequilibrium conditions are reached, the overall conditions determine thecrystalline phase of the powders.

[0125] A variety of ovens or the like can be used to perform theheating. An example of an apparatus 400 to perform this processing isdisplayed in FIG. 6. Apparatus 400 includes a jar 402, which can be madefrom glass or other inert material, into which the particles are placed.Suitable glass reactor jars are available from Ace Glass (Vineland,N.J.). The top of glass jar 402 is sealed to a glass cap 404, with aTeflon® gasket 405 between jar 402 and cap 404. Cap 404 can be held inplace with one or more clamps. Cap 404 includes a plurality of ports406, each with a Teflon® bushing. A multiblade stainless steel stirrer408 preferably is inserted through a central port 406 in cap 404.Stirrer 408 is connected to a suitable motor.

[0126] One or more tubes 410 are inserted through ports 406 for thedelivery of gases into jar 402. Tubes 410 can be made from stainlesssteel or other inert material. Diffusers 412 can be included at the tipsof tubes 410 to disburse the gas within jar 402. A heater/furnace 414generally is placed around jar 402. Suitable resistance heaters areavailable from Glas-col (Terre Haute, Ind.). One port preferablyincludes a T-connection 416. The temperature within jar 402 can bemeasured with a thermocouple 416 inserted through T-connection 416.T-connection 416 can be further connected to a vent 418. Vent 418provides for the venting of gas circulated through jar 402. Preferablyvent 418 is vented to a fume hood or alternative ventilation equipment.

[0127] Preferably, desired gases are flowed through jar 402. Tubes 410generally are connected to an oxidizing gas source and/or an inert gassource. Oxidizing gas, inert gas or a combination thereof to produce thedesired atmosphere are placed within jar 402 from the appropriate gassource(s). Various flow rates can be used. The flow rate preferably isbetween about 1 standard cubic centimeters per minute (sccm) to about1000 sccm and more preferably from about 10 sccm to about 500 scam. Theflow rate generally is constant through the processing step, althoughthe flow rate and the composition of the gas can be variedsystematically over time during processing, if desired. Alternatively, astatic gas atmosphere can be used.

[0128] VO₂, a material with a high melting point, is relatively easy toform in the laser pyrolysis apparatuses described above. VO₂ is asuitable starting product for oxidation to other forms of vanadiumoxide. Some empirical adjustment may be required to produce theconditions appropriate to generate a desired material. In addition, theheat processing can result in an alteration of the crystal latticeand/or removal of adsorbed compounds on the particles to improve thequality of the particles.

[0129] For the processing of vanadium oxide nanoparticles or metalvanadium oxide nanopartlcles, for example, the temperatures preferablyrange from about 50° C. to about 500° C. and more preferably from about60° C. to about 400° C. The heating preferably is continued for greaterthan about 5 minutes, and generally is continued for from about 2 hoursto about 100 hours, preferably from about 2 hours to about 50 hours.Some empirical adjustment may be required to produce the conditionsappropriate for yielding a desired material. The use of mild conditionsavoids interparticle sintering resulting in larger particle sizes. Somecontrolled sintering of the particles can be performed at somewhathigher temperatures to produce slightly larger, average particlediameters.

[0130] The conditions to convert crystalline VO₂ to orthorhombic V₂O₅and 2-D crystalline V₂O₅, and amorphous V₂O₅, to orthorhombic V₂O₅ and2-D crystalline V₂O₅ are describe in copending and commonly assignedU.S. patent application Ser. No. 08/897,903, to Bi et al., entitled“Processing of Vanadium Oxide Particles With Heat,” incorporated hereinby reference.

[0131] B. Thermal Processing for the Formation of Metal Vanadium OxideParticles

[0132] While metal vanadium oxide particles can be produced directlythrough laser pyrolysis, as described above, it has been discovered thatheat processing also can be used to form nanoscale metal vanadium oxideparticles. In a preferred approach to the thermal formation of metalvanadium oxide particles, vanadium oxide nanoscale particles first aremixed with a non-vanadium metal compound. The resulting mixture asheated in an oven to form a metal vanadium oxide composition. The heatprocessing to incorporate metal into the vanadium oxide lattice can beperformed in an oxidizing environment or an inert environment. In eithertype of environment, the heating step generally results in alteration ofthe oxygen to vanadium ratio. In addition, the heat processing canresult in an alteration of the crystal lattice and/or removal ofadsorbed compounds on the particles to improve the quality of theparticles.

[0133] The use of sufficiently mild conditions, i.e., temperatures wellbelow the melting point of the vanadium oxide particles, results inmetal incorporation into the vanadium oxide particles withoutsignificantly sintering the particles into larger particles. Thevanadium oxide particles used for the process preferably are nanoscalevanadium oxide particles. It has been discovered that metal vanadiumoxide compositions can be formed from vanadium oxides with an oxidationstate of +5 or less than +5. In particular, vanadium oxides with anoxidation states from +2 (VO) to +5 (V₂O₅) can be used to form metalvanadium oxide particles.

[0134] Generally, the metal incorporated into the metal vanadium oxideparticle is any non-vanadium transition metal. Preferred metals forincorporation into the vanadium oxide include, for example, copper,silver, gold, and combinations thereof. Suitable silver compoundsinclude, for example, silver nitrate (AgNO₃). Suitable copper compoundsinclude, for example, cupric nitrate (Cu(NO₃)₂). Alternatively, silvermetal powder, copper metal powder or gold metal powder can be used assources of the respective metals.

[0135] Appropriate oxidizing gases include, for example, O₂ (supplied asairs if desired), O₃, CO, CO₂ and combinations thereof. The reactant gascan be diluted with inert gases such as Ar, He and N₂. Alternatively,the gas atmosphere can be exclusively inert gas. Silver vanadium oxideparticles have been produced with either an inert atmosphere or anoxidizing atmosphere, as described in the Examples below.

[0136] A variety of apparatuses can be used to perform the heatprocessing for lithiation and/or annealing of a sample. An embodiment ofa suitable apparatus 400 is described above with respect to FIG. 6 forthe heat processing of vanadium oxides produced by laser pyrolysis. Analternative apparatus 430 for the incorporation of a metal into thevanadium oxide lattice is shown in FIG. 7. The particles are placedwithin a small vial 432, boat or the like within tube 434. Preferably,the desired gases are flowed through tube 434. Gases can be supplied forexample from inert gas source 436 or oxidizing gas source 438.

[0137] Tube 434 is located within oven or furnace 440. Oven 440 can beadapted from a commercial furnace, such as Mini-Mite™ 1100° C. TubeFurnace from Lindberg/Blue M, Asheville, N.C. Oven 440 maintains therelevant portions of the tube at a relatively constant temperature,although the temperature can be varied systematically through theprocessing step, if desired. The temperature can be monitored with athermocouple 442.

[0138] To form metal vanadium oxide particles in the heating step, amixture of vanadium oxide particles and the metal compound can be placedin tube 434 within a vial 432, boat or the like. Preferably, a solutionof the metal compound is mixed with the vanadium oxide nanoparticles andevaporated to dryness prior to further heating in the oven. Theevaporation can be performed simultaneously with the heating to form themetal vanadium oxide composition, if desired. For example, silvernitrate and copper nitrate can be applied to the vanadium oxideparticles as an aqueous solution. Alternatively, vanadium oxidenanoparticles can be mixed with a dry powder of the metal compound orelemental metal powder, thereby avoiding the evaporation step. Asufficient amount of the metal compound or elemental metal powder isadded to yield the desired amount of incorporation of the metal into thevanadium oxide lattice. This incorporation into the vanadium oxidelattice can be checked, for example, through the use of x-raydiffractometry, as described below.

[0139] The precise conditions including type of oxidizing gas (if any),concentration of oxidizing gas, pressure or flow rate of gas,temperature and processing time can be selected to produce the desiredtype of product material. The temperatures generally are mild, i.e.,significantly below the melting point of the materials. The use of mildconditions avoids interparticle sintering resulting in larger particlesizes. Some controlled sintering of the particles can be performed inthe oven at somewhat higher temperatures to produce slightly larger,average particle diameters.

[0140] For the metal incorporation into vanadium oxide, the temperaturegenerally ranges from about 50° C. to about 500° C., preferably fromabout 80° C. to about 400° C., and more preferably from about 80° C. toabout 325° C. The processing temperature can range from about 80° C. toabout 250° C. The particles preferably are heated for about 5 minutes toabout 100 hours. Some empirical adjustment may be required to producethe conditions appropriate for yielding a desired material.

[0141] C. Particle Properties

[0142] A collection of particles of interest, comprising metal vanadiumoxide compounds, generally has an average diameter for the primaryparticles of less than about 500 nm, preferably from about 5 nm to about100 nm, more preferably from about 5 nm to about 50 nm, and even morepreferably from about 5 nm to about 25 nm. The primary particles usuallyhave a roughly spherical gross appearance. Upon closer examination,crystalline particles generally have facets corresponding to theunderlying crystal lattice. Nevertheless, crystalline primary particlestend to exhibit growth that is roughly equal in the three physicaldimensions to give a gross spherical appearance. In preferredembodiments, 95 percent of the primary particles, and preferably 99percent, have ratios of the dimension along the major axis to thedimension along the minor axis less than about 2. Diameter measurementson particles with asymmetries are based on an average of lengthmeasurements along the principle axes of the particle.

[0143] Because of their small size, the primary particles tend to formloose agglomerates due to van der Waals and other electromagnetic forcesbetween nearby particles. Nevertheless, the nanometer scale of theprimary particles is clearly observable in transmission electronmicrographs of the particles. The particles generally have a surfacearea corresponding to particles on a nanometer scale as observed in themicrographs. Furthermore, the particles can manifest unique propertiesdue to their small size and large surface area per weight of material.For example, vanadium oxide nanoparticles generally exhibit surprisinglyhigh energy densities in lithium batteries, as described in copendingand commonly assigned U.S. patent application Ser. No. 08/897,776,entitled “Batteries With Electroactive Nanoparticles,” incorporatedherein by reference.

[0144] The primary particles preferably have a high degree of uniformityin size. Laser pyrolysis, as described above, generally results inparticles having a very narrow range of particle diameters. Furthermore,heat processing under mild conditions does not alter the very narrowrange of particle diameters. With aerosol delivery, the distribution ofparticle diameters is particularly sensitive to the reaction conditions.Nevertheless, if the reaction conditions are properly controlled, a verynarrow distribution of particle diameters can be obtained with anaerosol delivery system, as described above. As determined fromexamination of transmission electron micrographs, the primary particlesgenerally have a distribution in sizes such that at least about 95percent, and preferably 99 percent, of the primary particles have adiameter greater than about 40 percent of the average diameter and lessthan about 160 percent of the average diameter. Preferably, the primaryparticles have a distribution of diameters such that at least about 95percent, and preferably 99 percent, of the primary particles have adiameter greater than about 60 percent of the average diameter and lessthan about 140 percent of the average diameter.

[0145] Furthermore, in preferred embodiments no primary particles havean average diameter greater than about 4 times the average diameter andpreferably 3 times the average diameter, and more preferably 2 times theaverage diameter. In other words, the particle size distributioneffectively does not have a tail indicative of a small number ofparticles with significantly larger sizes. This is a result of the smallreaction region and corresponding rapid quench of the particles. Aneffective cut off in the tail of the size distribution indicates thatthere are less than about 1 particle in 10⁶ have a diameter greater thana specified cut off value above the average diameter. Narrow sizedistributions, lack of a tail in the distributions and the roughlyspherical morphology can be exploited in a variety of applications.

[0146] In addition, the nanoparticles generally have a very high puritylevel. The crystalline metal vanadium oxide nanoparticles produced bythe above described methods are expected to have a purity greater thanthe reactants because the crystal formation process tends to excludecontaminants from the lattice. Furthermore, crystalline vanadium oxideparticles produced by laser pyrolysis have a high degree ofcrystallinity. Similarly, the crystalline metal vanadium oxidenanoparticles produced by heat processing have a high degree ofcrystallinity. Impurities on the surface of the particles may be removedby heating the particles to achieve not only high crystalline purity buthigh purity overall.

[0147] Vanadium oxide has an intricate phase diagram due to the manypossible oxidation states of vanadium. Vanadium is known to exist inoxidation states between V⁺² and V⁺⁵. The energy differences between theoxides of vanadium in the different oxidation states is not large.Therefore, it is possible to produce stoichiometric mixed valencecompounds. Known forms of vanadium oxide include VO, VO_(1.27), V₂O₃,V₃O₅, VO₂, V₆O₁₃, V₄O₉, V₃O₇, and V₂O₅. Laser pyrolysis alone or withadditional heating can successfully yield single phase vanadium oxide inmany different oxidation states, as evidenced by x-ray diffractionstudies. These single phase materials are generally crystalline,although some amorphous nanoparticles have been produced. The heattreatment approaches are useful for increasing the oxidation state ofvanadium oxide particles or for converting vanadium oxide particles tomore ordered phases.

[0148] There are also mixed phase regions of the vanadium oxide phasediagram. In the mixed phase regions, particles can be formed that havedomains with different oxidation states, or different particles can besimultaneously formed with vanadium in different oxidation states. Inother words, certain particles or portions of particles have onestoichiometry while other particles or portions of particles have adifferent stoichiometry. Mixed phase nanoparticles have been formed.Non-stoichiometric materials also can be formed.

[0149] The vanadium oxides generally form crystals with octahedral ordistorted octahedral coordination. Specifically, VO, V₂O₃, VO₂, V₆O₁₃V₃O₇ can form crystals with octahedral coordination. In addition, V₃O₇can form crystals with trigonal bipyramidal coordination. V₂O₅ formscrystals with square pyramidal crystal structure. V₂O₅ recently also hasbeen produced in a two dimensional crystal structure. See, M. Hibino, etal., Solid State Ionics 79:239-244 (1995), incorporated herein byreference. When produced under appropriate conditions, the vanadiumoxide nanoparticles can be amorphous. The crystalline lattice of thevanadium oxide can be evaluated using x-ray diffraction measurements.

[0150] Metal vanadium oxide compounds can be formed with variousstoichiometries. U.S. Pat. No. 4,310,609 to Liang et al., entitled“Metal Oxide Composite Cathode Material for High Energy DensityBatteries,” incorporated herein by reference, describes the formation ofAg_(0.7)V₂O_(5.5), AgV₂O_(5.5), and Cu_(0.7)V₂O_(5.5). The production ofoxygen deficient silver vanadium oxide, Ag_(0.7)V₂O₅, is described inU.S. Pat. No. 5,389,472 to Takeuchi et al., entitled “Preparation ofSilver Vanadium Oxide Cathodes Using Ag(O) and V₂O₅ as StartingMaterials,” incorporated herein by reference. The phase diagram ofsilver vanadium oxides of the formula Ag_(x)V₂O_(y), 0.3≦x≦2.0,4.5≦y≦6.0, involving stoichiometric admixtures of V₂O₅ and AgVO₃, aredescribed in published European Patent Application 0 689 256A, entitled“Cathode material for nonaqueous electrochemical cells,” incorporatedherein by reference.

[0151] D. Batteries

[0152] Referring to FIG. 8, battery 450 has an negative electrode 452, apositive electrode 454 and separator 456 between negative electrode 452and positive electrode 454. A single battery can include multiplepositive electrodes and/or multiple negative electrodes. Electrolyte canbe supplied in a variety of ways as described further below. Battery 450preferably includes current collectors 458, 460 associated with negativeelectrode 452 and positive electrode 454, respectively. Multiple currentcollectors can be associated with each electrode if desired.

[0153] Lithium has been used in reduction/oxidation reactions inbatteries because it is the lightest metal and because it is the mostelectropositive metal. Certain forms of metal oxides are known toincorporate lithium ions into its structure through intercalation orsimilar mechanisms such as topochemical absorption. Intercalation oflithium ions can take place also into suitable forms of a vanadium oxidelattice as well as the lattice of metal vanadium oxide compositions.Suitable metal vanadium oxide nanoparticles for incorporation intobatteries can be produced by thermal processing of vanadium oxidenanoparticles with a metal compound or by direct laser pyrolysissynthesis of metal vanadium oxide nanoparticles with or withoutadditional heat processing.

[0154] In particular, lithium intercalates into the vanadium oxidelattice or metal vanadium oxide lattice during discharge of the battery.The lithium leaves the lattice upon recharging, i.e., when a voltage isapplied to the cell such that electric current flows into the positiveelectrode due to the application of an external EMF to the battery.Positive electrode 454 acts as a cathode during discharge, and negativeelectrode 452 acts as an anode during discharge of the cell. Metalvanadium oxide particles can be used directly in a positive electrodefor a lithium based battery to provide a cell with a high energydensity. Appropriate metal vanadium oxide particles can be an effectiveelectroactive material for a positive electrode in either a lithium orlithium ion battery.

[0155] Positive electrode 454 includes electroactive nanoparticles suchas metal vanadium oxide nanoparticles held together with a binder suchas a polymeric binder. Nanoparticles for use in positive electrode 454generally can have any shape, e.g., roughly spherical nanoparticles orelongated nanoparticles. In addition to metal vanadium oxide particles,positive electrode 454 can include other electroactive nanoparticlessuch as TiO₂ nanoparticles, vanadium oxide nanoparticles and manganeseoxide nanoparticles. The production of TiO₂ nanoparticles has beendescribed, see U.S. Pat. No. 4,705,762, incorporated herein byreference. Vanadium oxide nanoparticles are know to exhibit surprisinglyhigh energy densities, as described in copending and commonly assignedU.S. patent application Ser. No. 08/897,776, entitled “Batteries WithElectroactive Nanoparticles,” incorporated herein by reference. Theproduction of manganese oxide nanoparticles is described in copendingand commonly assigned U.S. patent application Ser. No. 09/188,770 toKumar et al. filed on Nov. 9, 1998, entitled “Metal Oxide Particles,”incorporated herein by reference.

[0156] While some electroactive materials are reasonable electricalconductors, a positive electrode generally includes electricallyconductive particles in addition to the electroactive nanoparticles.These supplementary, electrically conductive particles generally arealso held by the binder. Suitable electrically conductive particlesinclude conductive carbon particles such as carbon black, metalparticles such as silver particles, metal fibers such as stainless steelfibers, and the like.

[0157] High loadings of particles can be achieved in the binder.Particles preferably make up greater than about 80 percent by weight ofthe positive electrode, and more preferably greater than about 90percent by weight. The binder can be any of various suitable polymerssuch as polyvinylidene fluoride, polyethylene oxide, polyethylene,polypropylene, polytetrafluoro ethylene, polyacrylates,ethylene-(propylene-diene monomer) copolymer (EPDM) and mixtures andcopolymers thereof.

[0158] Negative electrode 452 can be constructed from a variety ofmaterials that are suitable for use with lithium ion electrolytes. Inthe case of lithium batteries, the negative electrode can includelithium metal or lithium alloy metal either in the form of a foil, gridor metal particles in a binder.

[0159] Lithium ion batteries use particles of a composition that canintercalate lithium. The particles are held with a binder in thenegative electrode. Suitable intercalation compounds include, forexample, graphite, synthetic graphite, coke, mesocarbons, doped carbons,fullerenes, niobium pentoxide, tin alloys, SnO₂ and mixtures andcomposites thereof.

[0160] Current collectors 458, 460 facilitate flow of electricity frombattery 450. Current collectors 458, 460 are electrically conductive andgenerally made of metal such as nickel, iron, stainless steel, aluminumand copper and can be metal foil or preferably a metal grid. Currentcollector 458, 460 can be on the surface of their associated electrodeor embedded within their associated electrode.

[0161] Separator element 456 is electrically insulating and provides forpassage of at least some types of ions. Ionic transmission through theseparator provides for electrical neutrality in the different sectionsof the cell. The separator generally prevents electroactive compounds inthe positive electrode from contacting electroactive compounds in thenegative electrode.

[0162] A variety of materials can be used for the separator. Forexample, the separator can be formed from glass fibers that form aporous matrix. Preferred separators are formed from polymers such asthose suitable for use as binders. Polymer separators can be porous toprovide for ionic conduction. Alternatively, polymer separators can besolid electrolytes formed from polymers such as polyethylene oxide.Solid electrolytes incorporate electrolyte into the polymer matrix toprovide for ionic conduction without the need for liquid solvent.

[0163] Electrolytes for lithium batteries or lithium ion batteries caninclude any of a variety of lithium salts. Preferred lithium salts haveinert anions and are nontoxic. Suitable lithium salts include, forexample, lithium hexafluorophosphate, lithium hexafluoroarsenate,lithiumbis(trifluoromethylsulfonyl imide), lithium trifluoromethanesulfonate, lithium tris(trifluoromethyl sulfonyl) methide, lithiumtetrafluoroborate, lithium perchlorate, lithium tetrachloroaluminate,lithium chloride and lithium perfluorobutane.

[0164] If a liquid solvent is used to dissolve the electrolyte, thesolvent preferably is inert and does not dissolve the electroactivematerials. Generally appropriate solvents include, for example,propylene carbonate, dimethyl carbonate, diethyl carbonate, 2-methyltetrahydrofuran, dioxolane, tetrahydrofuran, 1, 2-dimethoxyethane,ethylene carbonate, γ-butyrolactone, dimethyl sulfoxide, acetonitrile,formamide, dimethyl formamide and nitromethane.

[0165] The shape of the battery components can be adjusted to besuitable for the desired final product, for example, a coin battery, arectangular construction or a cylindrical battery. The battery generallyincludes a casing with appropriate portions in electrical contact withcurrent collectors and/or electrodes of the battery. If a liquidelectrolyte is used, the casing should prevent the leakage of theelectrolyte. The casing can help to maintain the battery elements inclose proximity to each other to reduce resistance within the battery. Aplurality of battery cells can be placed in a single case with the cellsconnected either in series or in parallel.

EXAMPLES Example 1 Production of Vanadium Oxide by Laser Pyrolysis

[0166] Single phase VO₂ particles were produced by laser pyrolysis. TheVOCl₃ (Strem Chemical, Inc., Newburyport, Mass.) precursor vapor wascarried into the reaction chamber by bubbling Ar gas through the VOCl₃liquid stored in a container at room temperature. The reactant gasmixture containing VOCl₃, Ar, O₂ and C₂H₄ was introduced into thereactant gas nozzle for injection into the reactant chamber. Thereactant gas nozzle had dimensions ⅝ in×⅛ in. C₂H₄ gas was used as alaser absorbing gas. Argon was used as an inert gas.

[0167] The synthesized vanadium oxide nanoscale particles can bedirectly handled in the air. Representative reaction conditions for theproduction of this material are described in Table 1. TABLE 1 Phase VO₂Crystal Monoclinic Structure Pressure 210 (Torr) Argon-Win 700 (sccm)Argon-Sld. 7.0 (slm) Ethylene (slm) 1.61 Carrier Gas- 1.4 Argon (slm)Oxygen (slm) 0.47 Precursor 40 Temp. (° C.) Production 35 Rate (gm/hr)Laser Power- 780 Input (watts) Laser Power- 640 Output (watts)

[0168] An x-ray diffractogram of representative product nanoparticles isshown in FIG. 9. Clear diffraction peaks corresponding to a monocliniccrystalline structure are visible. The identified structure from thediffractogram is almost identical to that of the corresponding bulkmaterial, which has larger particle sizes.

Example 2 Heat Treatment to Form Crystalline V₂O₅ Nanoparticles

[0169] The starting materials for the heat treatment were VO₂nanoparticles produced by laser pyrolysis according to the parameters inTable 1.

[0170] The nanoparticles were heat treated at in an oven roughly asshown in FIG. 6. The particles were fed in batches of between about 100grams to about 150 grams into the glass jar. Oxygen is fed through a ⅛″stainless steel tube at an oxygen flow rate of 155 cc/min. A mixingspeed of 5 rpm was used to constantly mix the powders during the heattreatment. The powders were heated for 30 minutes at 100° C., then for30 minutes at 200° C. and finally at 230° C. for 16 hours. A heatingrate of 4° C./minute was used to heat the samples to the targettemperatures. The resulting nanoparticles were single phase crystallineV₂O₅ nanoparticles. The x-ray diffractogram of this material is shown inFIG. 10. From the x-ray diffractogram, it could be determined that theresulting particles were orthorhombic V₂O₅.

[0171] TEM photographs were obtained of representative nanoparticlesfollowing heat treatment. The TEM photograph is shown in FIG. 11. Anapproximate size distribution was determined by manually measuringdiameters of the particles shown in FIG. 11. The particle sizedistribution is shown in FIG. 12. An average particle size of about10-11 nm was obtained. Only those particles showing clear particleboundaries were measured and recorded to avoid regions distorted in themicrograph. This should not bias the measurements obtained since thesingle view of the micrograph may not show a clear view of all particlesbecause of the orientation of the crystals.

Example 3 Heat Processing to Form Silver Vanadium Oxide From V₂O₅Nanoparticles

[0172] This example demonstrates the production of nanoscale silvervanadium oxide using a vanadium oxide nanoparticle starting material.The silver vanadium oxide is produced by heat processing.

[0173] About 9.5 g of silver nitrate (AgNO₃) (EM Industries, Hawthorne,N.Y.) was dissolved into about 15 ml of deionized water. Then, about 10g of V₂O₅ nanoparticles produced as described in Examples 2 were addedto the silver nitrate solution to form a mixture. The resulting mixturewas stirred on a magnetic stirrer for about 30 minutes. After thestirring was completed the solution was heated to about 160° C. in anoven to drive off the water The dried powder mixture was ground with amortar and pestle.

[0174] Six samples from the resulting ground powder weighing betweenabout 100 and about 300 mg of nanoparticles were placed separately intoan open 1 cc boat. The boat was placed within the quartz tube projectingthrough an oven to perform the heat processing. The oven was essentiallyas described above with respect to FIG. 7. Oxygen gas or argon gas wasflowed through a 1.0 in diameter quartz tube at a flow rate of about 20sccm. The samples were heated in the oven under the followingconditions: 1) 250° C., 60 hrs in argon 2) 250° C., 60 hrs in oxygen 3)325° C., 4 hrs in argon 4) 325° C., 4 hrs in oxygen 5) 400° C., 4 hrs inargon 6) 400° C., 4 hrs in oxygen.

[0175] The samples were heated at approximately the rate of 2° C./min.and cooled at the rate of approximately 1° C./min. The times given abovedid not include the heating and cooling time.

[0176] The structure of the particles following heating was examined byx-ray diffraction. The x-ray diffractograms for the samples heated inoxygen and in argon are shown in FIGS. 13 and 14, respectively. All ofthe heated samples produces diffractograms with peaks indicating thepresence of Ag₂V₄O₁₁. The samples heated at 400° C. appear to lacksignificant amounts of V₂O₅. Heating the samples for somewhat longertimes at the lower temperatures should eliminate any remaining portionsof the V₂O₅ starting material.

[0177] A transmission electron micrograph of the silver vanadium oxideparticles is shown in FIG. 15. For comparison, a transmission electronmicrograph of the V₂O₅ nanoparticle sample used to form the silvervanadium oxide nanoparticles is shown in FIG. 16, at the same scale asFIG. 15. The V₂O₅ nanoparticles in FIG. 16 were produced underconditions similar to the conditions described in Examples 1 and 2. Thesilver vanadium oxide particles in FIG. 15 surprisingly have a slightlysmaller average diameter than the vanadium oxide nanoparticle startingmaterial in FIG. 16.

Example 4 Heat Processing to Form Silver Vanadium Oxide From VO₂Nanoparticles

[0178] This example demonstrates the production of nanoscale silvervanadium oxide using a VO₂ vanadium oxide nanoparticle startingmaterial. The silver vanadium oxide is produced by heat processing.

[0179] VO₂ nanoparticles were produced under similar conditions asdescribed above in Example 1. Ten grams of nanocrystalline VO₂ powderwere washed with 500 ml of deionized water to remove any residualchlorine. The washing was performed in a Corning® 500 ml filter systemwith a 0.2 μm Nylon® membrane and a side arm for vacuum filtration. Thewashed nanocrystalline VO₂ powder was dried under vacuum at a pressureless than thirty inches of mercury (750 Torr) for a minimum of 12 hours,at a temperature between 100° C. and 120° C. The washed and driednanocrystalline VO₂ was shaken in a SPEX™ 8000 mixer/mill for 15 minutesto break up agglomerates.

[0180] Crystalline silver nitrate powder (99+purity) from EM Industries(Hawthorne, N.Y.) were added quantitatively to the deagglomerizednanocrystalline VO₂ powder in a ratio of one mole AgNO₃ for 2 moles ofVO₂. This powder mixture was ground in a Fritsch Mortar Grinder ModelP-2 (Gilson Company, Inc., Worthington, Ohio) for twenty minutes.Following grinding, the mixture was heated in a tube furnace,essentially as shown in FIG. 7, in a flowing oxygen atmosphere at a flowrate of 190 milliliters of oxygen per minute.

[0181] The heat treatment consisted of heating from room temperature to180° C. over an hour period, followed by an equilibration time of atleast one hour. Then, the temperature was increased gradually to atemperature of about 400° C. The temperature was held at the finaltemperature for about 20 hours. After heating at the final temperaturefor the desired period of time, the product was cooled to roomtemperature over a 5 to 15 hour period.

[0182] The crystal structure of the resulting powders were examined byx-ray diffraction. The x-ray diffractogram for the resulting material isshown in FIG. 17. The diffractogram has sharp peaks corresponding tosilver vanadium oxide (Ag₂V₄O₁₁).

[0183] The resulting silver vanadium oxide nanoparticles were furthercharacterized by differential scanning calorimetry (DSC). The DSCapparatus was a model Universal V2.3C DSC apparatus from TA Instruments,Inc., New Castle, Del. The measured heat flow as a function oftemperature is plotted in FIG. 18. The curve shows only two isotherms,corresponding to a peritectic transformation at about 558° and aeutectic point at about 545°. These transitions in silver vanadium oxideare described further in P. Fleury, Rev. Chim. Miner., 6(5) 819 (1969).

[0184] No lower temperature endotherms were observed. In particular, anendotherm at approximately 463°, corresponding to the melting of AgVO₃,was not observed. Thus, the DSC data suggests that the nanoscale silvervanadium oxide material was compositionally pure with respect to othermaterials having phase transitions up to the 600° C. limit of the DSCtest.

[0185] This dry powder mixing approach was also used successfully toproduce silver vanadium oxide nanoparticles from a mixture ofnanocrystalline V₂O₅ and crystalline silver nitrate powders, except thatthe washing step generally is unnecessary since nanocrystalline V₂O₅nanoparticles produced in a heat treatment process do not containresidual chlorine. Furthermore, the molar ratios are adjustedaccordingly.

Example 5 Direct Laser Pyrolysis Synthesis of Nanoscale Silver—VanadiumOxide Materials

[0186] The synthesis of nanoscale silver—vanadium oxide materialsdescribed in this example was performed by laser pyrolysis. Theparticles were produced using essentially the laser pyrolysis apparatusof FIG. 1, described above, using the reactant delivery apparatus ofFIG. 3A.

[0187] The solution for delivery as an aerosol in the reaction chamberwas produced with a vanadium precursor solution. To produce the vanadiumprecursor solution, first a 20.0 g sample of vanadium (III) oxide (V₂O₃)from Aldrich Chemical (Milwaukee, Wis.) was suspended in 240 ml ofdeionized water. A 60 ml quantity of 70% by weight aqueous nitric acid(HNO₃) solution was added dropwise to the vanadium (III) oxidesuspension with vigorous stirring. Caution was taken because thereaction with nitric acid is exothermic and liberates a brown gassuspected to be NO₂. The resulting vanadium precursor solution was adark blue solution.

[0188] To produce the precursor solution for aerosol delivery, asolution of silver nitrate (AgNO₃) was prepared by dissolving 22.7 g ofsilver nitrate from Aldrich Chemical (Milwaukee, Wis.) in a 200 mlvolume of deionized water. To prepare a solution of metal mixtures foraerosol delivery, the silver nitrate solution was added to the vanadiumprecursor solution with constant stirring. The resulting dark bluesolution had a molar ratio of vanadium to silver of about 2:1.Experiments using higher relative amounts of silver yielded comparableresults.

[0189] The aqueous solution with the vanadium and silver precursors wascarried into the reaction chamber as an aerosol. C₂H₄ gas was used as alaser absorbing gas, and Argon was used as an inert gas. O₂, Ar and C₂H₄were delivered into the gas supply tube of the reactant supply system.The reactant mixture containing vanadium oxide, silver nitrate, Ar, O₂and C₂H₄ was introduced into the reactant nozzle for injection into thereaction chamber. The reactant nozzle had an opening with dimensions of⅝ in.×¼ in. Additional parameters of the laser pyrolysis synthesisrelating to the particles of Example 1 are specified in Table 2. TABLE 21 Crystal Structure Mixed Phase Pressure (Torr) 450 Argon-Window (SLM)2.00 Argon-Shielding (SLM) 9.81 Ethylene (SLM) 0.73 Argon (SLM) 4.00Oxygen (SLM) 0.96 Laser Power (input) 490-510 (Watts) Laser Power(output) 450 (Watts) Vanadium/Silver Mole 2:1 Ratio PrecursorTemperature ° C. Room Temperature

[0190] To evaluate the atomic arrangement, the samples were examined byx-ray diffraction using the Cu(Kα) radiation line on a Siemens D500x-ray diffractometer. X-ray diffractograms for a sample produced underthe conditions specified in Table 2 are shown in FIG. 19. Thediffractogram has peaks that can be identified as VO₂, V₂O₃, andelemental silver. Additional peaks in the diffractograms of have notbeen correlated with known materials and are discussed further inExample 7.

[0191] Powders of a sample produced under the conditions of Table 2 werefurther analyzed using transmission electron microscopy. The TEMmicrograph is shown in FIG. 20. The TEM micrograph has a particlesfalling within different size distributions. This is characteristic ofmixed phase materials made by laser pyrolysis, where each materialgenerally has a very narrow particle size distribution.

[0192] Furthermore, as described in the following Example, heattreatment of these nanoscale silver—vanadium oxide materials in anoxygen environment can result in crystalline Ag₂V₄O₁₁ in high yields.

Example 6 Heat Treatment of Laser Pyrolysis Produced NanoscaleSilver—Vanadium Oxide Materials

[0193] This example demonstrates the production of nanoscale crystallinesilver vanadium oxide Ag₂V₄O₁₁ starting with nanoscale silver—vanadiumoxide materials produced by laser pyrolysis, as described in Example 5.

[0194] A sample silver—vanadium oxide powder corresponding to a samplefrom Example 5 weighing between about 300 and about 700 mg ofnanoparticles were placed into an open 1 cc boat. The boat was placedwithin the quartz tube projecting through an oven to perform the heatprocessing. The oven was essentially as described above with respect toFIG. 7. Oxygen gas was flowed through a 1.0 in diameter quartz tube at aflow rate of about 30 sccm.

[0195] The heat treatment consisted of heating from room temperature to180° C. over an hour period, followed by an equilibration time of atleast one hour. Then, the temperature was increased approximately at arate of 3° C. per minute to a temperature of about 360° C. Thetemperature was held at the final temperature for 16.5 hours. Afterheating at the final temperature for the desired period of time, theproduct was cooled to room temperature at a rate of about 1 degree perminute. The heating time given above did not include the heating andcooling time.

[0196] The structure of the particles following heating was examined byx-ray diffraction. The x-ray diffractograms for the sample followingheating is shown in FIG. 21. The heat treated powders were also examinedby transmission electron microscopy. A TEM micrograph of the samples isshown in FIG. 22.

Example 7 Direct Laser Pyrolysis Synthesis of Silver Vanadium OxideNanoparticles

[0197] The syntheses of silver vanadium oxide nanoparticles described inthis example was performed by laser pyrolysis. The particles wereproduced using essentially the laser pyrolysis apparatus of FIG. 1,described above, using the reactant delivery apparatus of FIGS. 3A or3B.

[0198] Two solutions were prepared for delivery into the reactionchamber as an aerosol. Both solutions were produced with comparablevanadium precursor solutions. To produce the first vanadium precursorsolution, a 10.0 g sample of vanadium (III) oxide (V₂O₃) from AldrichChemical (Milwaukee, Wis.) was suspended in 120 ml of deionized water. A30 ml quantity of 70% by weight aqueous nitric acid (HNO₃) solution wasadded dropwise to the vanadium (III) oxide suspension with vigorousstirring. Caution was taken because the reaction with nitric acid isexothermic and liberates a brown gas suspected to be N0 ₂. The resultingvanadium precursor solution (about 150 ml) was a dark blue solution. Thesecond vanadium precursor solution involved the scale-up of the firstprecursor solution by a factor of three in all ingredients.

[0199] To produce a first silver solution, a solution of silvercarbonate (Ag₂CO₃) from Aldrich Chemical (Milwaukee, Wis.) was preparedby suspending 9.2 g of silver carbonate in a 100 ml volume of deionizedwater. A 10 ml quantity of 70% by weight aqueous nitric acid (HNO₃) wasadded dropwise with vigorous stirring. A clear colorless solutionresulted upon completion of the addition of nitric acid. To produce afirst metal mixture solution for aerosol delivery, the silver solutionwas added to the first vanadium precursor solution with constantstirring. The resulting dark blue first metal mixiure solution had amolar ratio of vanadium to silver of about 2:1.

[0200] To produce a second silver solution, 34.0 g of silver nitrate(AgNo₃) from Aldrich Chemical (Milwaukee, Wis.) was dissolved in a 300ml volume of deionized water. To prepare a second solution of metalmixtures for aerosol delivery, the silver nitrate solution was added tothe second vanadium precursor solution with constant stirring. Theresulting dark blue second metal mixture solution also had a molar ratioof vanadium to silver of about 2:1.

[0201] The selected aqueous solution with the vanadium and silverprecursors was carried into the reaction chamber as an aerosol. C₂H₄ gaswas used as a laser absorbing gas, and Argon was used as an inert gas.O₂, Ar and C₂H₄ were delivered into the gas supply tube of the reactantsupply system. The reactant mixture containing vanadium oxide, silvernitrate, Ar, O₂ and C₂H₄ was introduced into the reactant nozzle forinjection into the reaction chamber. The reactant nozzle had an openingwith dimensions of ⅝ in.×¼ in. Additional parameters of the laserpyrolysis synthesis relating to the particle synthesis are specified inTable 3. Sample 1 was prepared using the reactant delivery systemessentially as shown in FIG. 3A while sample 2 was prepared using thereactant delivery system essentially as shown in FIG. 3B. TABLE 3 1 2Crystal Structure Mixed Phase Mixed Phase Pressure (Torr) 600 600Argon-Window (SLM) 2.00 2.00 Argon-Shielding (SLM) 9.82 9.86 Ethylene(SLM) 0.74 081 Argon (SLM) 4.00 4.80 Oxygen (SLM) 0.96 1.30 Laser Power(input) 490-531 390 (Watts) Laser Power (output) 445 320 (Watts)Precursor Solution 1 2 Precursor Temperature Room Room ° C. TemperatureTemperature

[0202] To evaluate the atomic arrangement, the samples were examined byx-ray diffraction using the Cu(Kα) radiation line on a Siemens D500x-ray diffractometer. X-ray diffractograms for samples 1 (lower curve)and 2 (upper curve) produced under the conditions specified in Table 3are shown in FIG. 23. The samples had peaks corresponding to VO₂,elemental silver and peaks that did not correspond to known materials. Asignificant crystalline phase for these samples had peaks at 2 θ equalto about 30-31°, 32, 33 and 35. This phase is thought to be a previouslyunidentified silver vanadium oxide phase. This phase is observed insamples prepared by mixing vanadium oxide nanoparticles and silvernitrate under conditions where the samples are heated for aninsufficient time period to produce Ag₂V₄O₁₁. Specific capacitymeasurements of sample 1 in a coin cell, presented below, are consistentwith this interpretation. These peaks in smaller amounts are alsoobserved in the samples produced under the conditions described inExample 5.

[0203] Powders of samples produced under the conditions specified inTable 3 were further analyzed using transmission electron microscopy.The TEM micrographs are shown in FIGS. 24A (first column of Table 3) and24B (second column of Table 3). The TEM micrograph has a particlesfalling within different size distributions. This is characteristic ofmixed phase materials made by laser pyrolysis, where each materialgenerally has a very narrow particle size distribution. The portion ofsilver vanadium oxide in the mixed phase material should be increased byan increase in oxygen flow, a decrease in laser power and an increase inpressure.

Example 8 Direct Laser Pyrolysis Synthesis of Silver Vanadium OxideNanoparticles

[0204] The synthesis of silver vanadium oxide nanoparticles described inthis example was performed by laser pyrolysis. The particles wereproduced using essentially the laser pyrolysis apparatus of FIG. 1,described above, using the reactant delivery apparatus of FIG. 3B.

[0205] A solution was prepared for delivery into the reaction chamber asan aerosol. To produce the first vanadium precursor solution, a 20.0 gsample of vanadium (III) oxide (V₂O₃) from Aldrich Chemical (Milwaukee,Wis.) was suspended in 240 ml of deionized water. A 60 ml quantity of70% by weight aqueous nitric acid (HNO₃) solution was added dropwise tothe vanadium (III) oxide suspension with vigorous stirring. Caution wastaken because the reaction with nitric acid is exothermic and liberatesa brown gas suspected to be NO₂. The resulting vanadium precursorsolution (about 300 ml) was a dark blue solution.

[0206] Five different silver solutions were prepared to produce asolution for aerosol delivery with varying ratios of silver to vanadium.To produce the silver solutions, a quantity of silver nitrate (AgNO₃)from Aldrich Chemical (Milwaukee, Wis.) was dissolved in a 200 ml volumeof deionized water. The five silver solutions had the following grams ofsilver nitrate: 1) 15.9 g, 2) 18.1 g, 3) 20.4 g, 4) 22.7 g, 5) 23.8 g.To prepare solutions of metal mixtures for aerosol delivery, the silvernitrate solution was added to a vanadium precursor solution withconstant stirring. The resulting dark blue second metal mixturesolution. The five solutions had the following molar ratio of silver tovanadium: 1) 0.7:2, 2) 0.8:2, 3) 0.9:2, 4) 1.0:2, 5) 1.05:2.

[0207] The selected aqueous solution with the vanadium and silverprecursors was carried into the reaction chamber as an aerosol. C₂H₄ gaswas used as a laser absorbing gas, and Argon was used as an inert gas.O₂, Ar and C₂H₄ were delivered into the gas supply tube of the reactantsupply system. The reactant mixture containing vanadium oxide, silvernitrate, Ar, O₂ and C₂H₄ was introduced into the reactant nozzle forinjection into the reaction chamber. The reactant nozzle had an openingwith dimensions of ⅝ in.×¼ in. Additional parameters of the laserpyrolysis synthesis relating to the particle synthesis are specified inTable 4. TABLE 4 Crystal Structure Mixed Phase Pressure (Torr) 600Argon-Window (SLM) 2.00 Argon-Shielding (SLM) 9.86 Ethylene (SLM) 0.81Argon (SLM) 0.80 Oxygen (SLM) 1.30 Laser Power (input) 390 (Watts) LaserPower (output) 320 (Watts) Precursor Temperature Room ° C. Temperature

[0208] To evaluate the atomic arrangement, the samples were examined byx-ray diffraction using the Cu(Kα) radiation line on a Siemens D500x-ray diffractometer. X-ray diffractograms for samples 1-5 producedunder the conditions specified in Table 4 are shown in FIG. 25. Thesamples had peaks corresponding to VO₂, elemental silver, possibly V₂O₃and peaks that did not correspond to known materials. A significantcrystalline phase for these samples had peaks at 2 θ equal to about30-31°, 32, 33 and 35. As noted above, this phase is thought to be apreviously unidentified silver vanadium oxide phase. Under theseconditions, as the silver to vanadium ratio increased, the peakscorresponding to vanadium oxide decreased. Evidently, additionalamorphous components containing vanadium, oxygen and possibly silverwere produced when the relative amount of silver was increased.

Example 9 Laser Pyrolysis Production of Elemental Silver Nanoparticles

[0209] The synthesis of elemental silver nanoparticles described in thisexample was performed by laser pyrolysis. The particles were producedusing essentially the laser pyrolysis apparatus of FIG. 1, describedabove, using the reactant delivery apparatus of FIG. 3A.

[0210] A 1 molar silver nitrate solution was prepared for delivery intothe reaction chamber as an aerosol by dissolving 50.96 g of silvernitrate (Aldrich Chemical, Milwaukee, Wis.) into 300 ml deionized waterto produce a clear solution. C₂H₄ gas was used as a laser absorbing gas,and Argon was used as an inert gas. O₂, Ar and C₂H₄ were delivered intothe gas supply tube of the reactant supply system. The reactant mixturecontaining silver nitrate, Ar, O₂ and C₂H₄ was introduced into thereactant nozzle for injection into the reaction chamber. The reactantnozzle had an opening with dimensions of ⅝ in.×¼ in. Additionalparameters of the laser pyrolysis synthesis relating to the particlesynthesis are specified in Table 5. TABLE 5 1 2 face centered facecentered Crystal Structure cubic cubic Pressure (Torr) 450 450Argon-Window (SLM) 2.00 2.00 Argon-Shielding (SLM) 9.82 9.82 Ethylene(SLM) 1.342 0.734 Argon (SLM) 5.64 3.99 Oxygen (SLM) 1.41 0.96 LaserPower (input) 970 490 (Watts) Laser Power (output) 800 450 (Watts)Production Rate 1.44 1.02 (gram/hour) Precursor Temperature Room Room °C. Temperature Temperature

[0211] To evaluate the atomic arrangement, the samples were examined byx-ray diffraction using the Cu(Kα) radiation line on a Siemens D500x-ray diffractometer. X-ray diffractograms for sample 1 and sample 2produced under the conditions specified in Table 5 are shown in FIGS. 26and 27, respectively. The samples had strong peaks corresponding toelemental silver.

[0212] Powders produced under the conditions of column 1 of Table 5 werefurther analyzed using transmission electron microscopy. The TEMmicrograph is shown in FIG. 28. The particle size distribution in theTEM micrograph is broad relative to particle size distributionsinvolving laser pyrolysis synthesis. The particle size distribution canbe narrowed significantly by either using gas phase precursors or a moreuniform aerosol delivery.

[0213] Representative particles were also analyzed by elementalanalysis. A typical elemental analysis of these materials yielded inweight percent about 93.09% silver, 2.40% carbon, 0.05% hydrogen, and0.35% nitrogen. Oxygen was not directly measured and may have accountedfor some of the remaining weight. The elemental analysis was performedby Desert Analytics, Tucson, Ariz.

[0214] The carbon component in the nanoparticles likely is in the formof a coating. Such carbon coatings can be formed from the carbonintroduced by ethylene within the reactant stream. Generally, the carboncan be removed by heating under an oxidizing atmosphere under mildconditions. The removal of such carbon coatings is described further incopending and commonly assigned, U.S. patent application Ser. No.09/123,255, entitled “Metal (Silicon) Oxide/Carbon Composite Particles,”incorporated herein by reference.

[0215] Since other group IB elements, copper and gold, have similarchemical properties as silver, substitution of copper or gold precursorsfor the silver precursors under similar conditions should result in theproduction of elemental copper or gold nanoparticles.

Example 10 Lithium Batteries Formed With Silver Vanadium OxideNanoparticles

[0216] This example demonstrates the suitability of silver vanadiumoxide particles for the production of lithium based batteries and theattainability of an increased capacity.

[0217] To produce a test cell incorporating silver vanadium oxideproduced according to one of the Examples above, a desired quantity ofsilver vanadium oxide nanoparticles was weighed and combined withpredetermined amounts of graphite powder (Chuetsu Graphite Works, CO.,Osaka, Japan) and acetylene black powder (Catalog number 55, ChevronCorp.) as conductive diluents, and a 60% by weight dispersion of Teflon®(Catalog No. 44,509-6, Aldrich Chemical Co., Milwaukee, Wis.) in wateras a binder. The mixture included 70% by weight silver vanadium oxidenanoparticles, 10% by weight graphite, 10% by weight acetylene black,and 10% by weight Teflon®. The resulting combination was mixed well,kneaded, and rolled into a one-millimeter thick sheet. An approximatelytwo-square centimeter area disk was cut from the sheet. The disk wasthen dried and pressed in a 1.6 cm diameter die set at 12,000 pounds for45-60 seconds to form a dense pellet The pressed pellet was vacuum driedand weighed.

[0218] The pressed and dried disk was used as the active cathode in a2025 coin cell. To form the coin cell, a 1.6 square centimeter disk ofnickel expanded metal was punched and resistance welded as a currentcollector to the inside of the stainless steel cover of the 2025 coincell hardware (catalog No. 10769, Alfa Aesar, Inc., Ward Hill, Mass.).Battery grade lithium foil (0.75 mm thick) from Hohsen Corp. (OsakaJapan) was punched into a two-square centimeter disk and cold welded tothe nickel expanded metal. A microporous polypropylene separator disk(Celgard® 2400, Hoechst-Celanese, Charlotte, N.C.) of appropriatedimensions was placed over the lithium disk.

[0219] A predetermined amount of electrolyte was added to thisseparator/lithium assembly. The electrolyte solution was composed of 1MLiPF₆ salt. The solvent for the electrolyte solution was a 1:1 volumeratio of ethylene carbonate to dimethyl carbonate. A second 1.6 squarecentimeter disk of stainless steel expanded metal was punched andresistance welded to the inside of the stainless steel can of the 2025coin cell hardware. The active cathode pellet was placed on the nickelexpanded metal and mated with the above separator/lithium assembly. Thestainless steel can and stainless steal cover are separated from eachother by a polypropylene grommet. The mated assembly was crimpedtogether and employed as a test coin cell.

[0220] The measurements were controlled by a Maccor Battery Test System,Series 4000, from Maccor, Inc. (Tulsa, Okla.). The discharge profile wasrecorded, and the discharge capacity of the active material wasobtained.

[0221] To form a first coin cell, a cathode pellet was formed from 0.143g of nanoscale silver vanadium oxide formed by heat processing ofnanoscale VO₂ and silver nitrate, as described above in Example 4. Theopen circuit voltage immediately after crimping was 3.53 volts. The cellwas placed in a controlled atmosphere chamber at 37±1 degrees C. andallowed to equilibrate for 4 hours. Then, the cell was subjected to aconstant current discharge of 0.1 milliamperes per square centimeters ofactive interfacial electrode surface area. When the voltage reached 1.0volt, the discharge current was allowed to decay as the cell voltage washeld at 1.0 volt for five hours. The 1.0 volt discharge allows for acapacity measurement independent of polarization effects that resultfrom discharge at finite values of current. This yields a capacitymeasurement that more closely approximates the maximum value that wouldbe obtained with by discharging the battery at infinitely slowdischarge.

[0222] The voltage as a function of time is plotted in FIG. 29. Thefirst four hours in the plot were taken during temperature equilibrationand do not involve any battery discharge. A plot of voltage as afunction of cumulative capacity is plotted in FIG. 30. The cumulativedischarge capacity was measured as 51.0 milliampere-hours, or a specificcapacity of about 357 milliampere hours per gram of active silvervanadium oxide nanoparticles. This is greater than the theoreticalspecific capacity.

[0223] A second cell was constructed as described above with silvervanadium oxide as directly synthesized, as described above in Example 5.The cathode contained 0.148 g of nanoscale silver vanadium oxideparticles. The open circuit voltage immediately after crimping was 3.3volts. The cell was placed in a controlled atmosphere chamber at 37±1degrees, allowed to equilibrate for 4 hours. The cell was subjected to aconstant current discharge of 0.309 milliamperes per square centimeterof active interfacial electrode surface area. When the voltage reached1.0 volt, the discharge current was allowed to decompose as the cellvoltage was held at 1.0 volt for five hours.

[0224] The voltage-time results are illustrated in FIG. 31. The firstfour hours in the plot were taken during temperature equilibration anddo not involve any battery discharge. A plot of voltage versuscumulative capacity is given in FIG. 32. As illustrated, the cumulativedischarge capacity was measured at 15.4 milliampere-hours, or specificcapacity of approximately 104.3 milliampere-hours per gram of activesilver vanadium oxide nanoparticles. The discharge capacity wasevaluated by the integral over the discharge time of the voltagemultiplied by the current divided. The specific capacity was evaluatedas the discharge capacity divided by the mass of the active material.

[0225] A third cell was constructed as described above with silvervanadium oxide synthesized by laser pyrolysis with subsequent annealingin an oven, as described above in Example 6. The active cathode pelletcontained 0.157 g of silver vanadium oxide nanoparticles. The open cellvoltage immediately after crimping was 3.5 volts. The cell was placed ina controlled atmosphere chamber at 37±1° C. and allowed to equilibratefor 4 hours. Then, the cell was subjected to a constant currentdischarge of 0.100 milliamperes per square centimeter of activeinterfacial electrode surface area. When the voltage reached 1.0 volt,the discharge current was allowed to decompose as the cell voltage washeld at 1.0 volt for five hours.

[0226] The voltage-time results are illustrated in FIG. 33. The firstfour hours in the plot were taken during temperature equilibration anddo not involve any battery discharge. A plot of voltage versuscumulative capacity is given in FIG. 34. As illustrated, the cumulativedischarge capacity was measured at 63.53 milliampere-hours, or aspecific capacity of approximately 404 milliampere-hours per gram ofactive silver vanadium oxide nanoparticles.

[0227] A fourth cell was constructed as described above with silvervanadium oxide synthesized by laser pyrolysis, as described above inExample 7 under conditions specified in the first column of Table 3. Theactive cathode pellet contained 0.154 g of silver vanadium oxidenanoparticles. The open cell voltage immediately after crimping was 3.4volts. The cell was placed in a controlled atmosphere chamber at 37±1°C. and allowed to equilibrate for 4 hours. Then, the cell was subjectedto a constant current discharge of 0.309 milliamperes per squarecentimeter of active interfacial electrode surface area. When thevoltage reached 1.0 volt, the discharge current was allowed to decomposeas the cell voltage was held at 1.0 volt for five hours.

[0228] The voltage-time results are illustrated in FIG. 35. The firstfour hours in the plot were taken during temperature equilibration anddo not involve any battery discharge. A plot of voltage versuscumulative capacity is given in FIG. 36. The voltage plots shown inFIGS. 35 and 36 have a shape characterized by silver vanadium oxidesignatures. As illustrated, the cumulative discharge capacity wasmeasured at 35.54 milliampere-hours, or a specific capacity ofapproximately 230 milliampere-hours per gram of active silver vanadiumoxide nanoparticles. The low specific capacity suggests that the silvervanadium oxide particles were part of a mixed phase material.

[0229] A theoretical capacity of 315 milliampere-hours per gram (7equivalents of lithium) for Ag₂V₄O₁₁ has been reported, see Takeuchi etal., “The Reduction of Silver Vanadium Oxide in Lithium/Silver VanadiumOxide Cells, J. Electrochem. Soc. 135:2691 (November 1988) and Leisinget al., Journal of Power Sources 68:730-734 (1997), both of which areincorporated herein by reference Thus, value of specific capacityobtained in the Examples described herein significantly exceed thetheoretical values.

[0230] The embodiments described above are intended to be illustrativeand not limiting. Additional embodiments are within the claims below.Although the present invention has been described with reference topreferred embodiments, workers skilled in the art will recognize thatchanges may be made in form and detail without departing from the spiritand scope of the invention.

What is claimed is:
 1. A method for producing metal vanadium oxideparticles comprising reacting a reactant stream comprising a vanadiumprecursor, and a second metal precursor in a reaction chamber, where thereaction is driven by energy absorbed from an electromagnetic field. 2.The method of claim 1 wherein the reactant stream further comprises areactant that is an oxygen source.
 3. The method of claim 1 wherein thereactant stream further comprises a radiation absorbing compound.
 4. Themethod of claim 1 wherein the vanadium precursor within the reactantstream is in the form of an aerosol.
 5. The method of claim 1 whereinthe second metal precursor within the reactant stream is in the form ofan aerosol.
 6. The method of claim 1 wherein both the vanadium precursorand the second metal precursor within the reactant stream are in theform of an aerosol.
 7. The method of claim 1 wherein the metal vanadiumoxide particles have an average diameter from about 5 nm to about 100nm.
 8. The method of claim 1 wherein the metal vanadium oxide particlescomprise silver vanadium oxide, Ag_(x)V₂O_(y), 0.3≦x≦2.0, 4.5≦y≦6.0. 9.The method of claim 1 wherein the metal vanadium oxide particlescomprise Ag₂V₄O₁₁.
 10. The method of claim 1 wherein effectively nometal vanadium oxide particles have a diameter greater than about fourtimes the average diameter of the collection of particles.
 11. Themethod of claim 1 wherein the metal vanadium oxide particles have adistribution of particle sizes such that at least about 95 percent ofthe particles have a diameter greater than about 40 percent of theaverage diameter and less than about 160 percent of the averagediameter.
 12. The method of claim 1 wherein the second metal precursorcomprises silver cations.
 13. The method of claim 1 wherein the vanadiumprecursor comprises vanadium cations.
 14. A battery comprising a cathodehaving active particles comprising silver vanadium oxide and a binder,the positive electrode exhibiting an energy density of greater thanabout 340 milliampere hours per gram of active particles when dischargedto about 1.0V.
 15. The battery of claim 14 wherein the active particleshave an average diameter from about 5 nm to about 100 nm.
 16. Thebattery of claim 14 wherein the silver vanadium oxide comprises silvervanadium oxide, Ag_(x)V₂O_(y), 0.3≦x≦2.0, 4.5≦y≦6.0.
 17. The battery ofclaim 16 wherein the silver vanadium oxide comprises Ag₂V₄O₁₁.
 18. Thebattery of claim 14 wherein the cathode further comprises supplementary,electrically conductive particles.
 19. The battery of claim 14 whereinthe cathode exhibits an energy density of greater than about 350milliampere hours per gram of active particles.
 20. An implantabledefibrillator comprising a lithium based battery having a cathodecomprising silver vanadium oxide with an energy density upon dischargeto about 1.0V of greater than about 340 milliampere hours per gram ofcathode active material.
 21. A battery comprising a cathode havingactive particles comprising metal vanadium oxide and a binder, thepositive electrode exhibiting an energy density of greater than about400 milliampere hours per gram of active particles when discharged toabout 1.0V.
 22. A method of producing a composite of elemental metalnanoparticles and vanadium oxide nanoparticles, the method comprisingreacting a reactant stream comprising a vanadium precursor, and a secondmetal precursor in a reaction chamber, where the reaction is driven byenergy absorbed from an electromagnetic field.
 23. A method forproducing metal vanadium oxide particles comprising reacting a reactantstream comprising a vanadium precursor, and a second metal precursor ina reaction chamber, where the reaction is driven by energy absorbed froma combustion flame.
 24. A method of producing particles comprising a anelemental metal selected from the group consisting copper, silver andgold, the method comprising reacting a molecular stream in a reactionchamber, the molecular stream comprising a metal precursor and aradiation absorber, where the reaction is driven by electromagneticradiation.